Article beginning on page 112.
Psyche 6:112-114, 1891.

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PSYCHE.
[July 1891.
Seventh stage (2 larvae only). Head
pale yellow minutely mottled with grayish spots; labrum, antennae and a spot before the eyes, white; ocelli and jaws black; width 3.5 mm. The body is as in the previous
stage, but the warts on the cervical shield are not distinctly darker. The dorsal black- ish or pale gray bhade is in triplicate on joints 3 an4 4. Spiracles white in a fine black border. The body is often bright yel- low, as are the doi-bal tufts, and even the hair is yellowis-h.
Cocoon. Double, thin, made of silk and
the hairs of the larva.
$ Pzifi.
Cylindrical, the abdominal seg-
ments tapering, the eyes, wing caves and an- tenna cases especially prominent; a little depressed behind the thorax. Seini-trans- parent, shiny yellowish white, the back cov- ered with long, thin, silky white hairs; cre- master flat, terminating in several brown hooks well fastened in the silk of the cocoon. Length 12 mm.; width 5 mm.
Pupa. Robust, thickest through the
and to 4th abdominal begments, elbewhere smaller, of nearly even width; thorax and head small, no wing cases, leg cases small. Last segment rounded, cremaster flat, rather broad at base, terminating in a number of brown divergent hooks. Color seinitrans- parent, bhiny, very pale yellowish, without marks. Over the dorsum considerable fine, rather long, whitibh silky hair. Length 18 mm.. greatest diameter 8 mm.
$ Imago. Of the same structure as 0.
lcuco.<rtigma, but not white, the color of the down, which is especially abundant on the ventral side, being light brown. A small black spot on the second abdominal segment. The rudimentary wings ale dark cinereous. The 8 imago is very himilar to 0. leucostig- ma, but can be distinguished by its daiker color and heavier black markings.
Foodfilants. Dr Thaxter gives oak, but I have found the species as omnivorous as 0. Zeucosti'gma. My specimens were fed mainly on maple and witch-hazel.
THE GERM-BAND OF INSECTS.*
Those who have watched the advance in
our knowledge of. insect embryology during the past three or four years will be deeply interested in Prof. Graber's latest treatise. Like his muscid paper it represents many years' study, but unlike that work it covers a very considerable ground, being a compre- hensive description of the germ-band of a number of insects. The species investigated belong to the genera: Lina, Lema, Tele-
phorus, Melolontha, Hydrophilus; Pieris, Gastropacha, Bombyx, Zygaena ; Hylotoma; Stenobothrus, Mantis, and Gryllotalpa. It will be seen that this list comprises repre- * Vergleichende studien am keimslreif der insect~n, von Veit Gr.iber. Denkschr. d. math. naturwiss. +se d. k. akad. d. wiss. Wien. Ed. 57, 1890,621- 734. 12 colored plates. 4'.
sentatives of four of the important orders. Prof. GI-aber treats of the formation and method of growth of the germ-band, its re- lations to the envelopes (amnion and serosa), its segmentation (both internal and external) and its appendages. Chapters are introduced on the formation of the germ-layers and on the origin of the body spaces. Many pages are given up to a minute and critical dibcus- sion of the results achieved by other investi- gators. The work concludes with a long
chapter on the development of the nervous system.
In a brief sketch we cannot hope to do
justice to the muss of matter with which Prof. Graber presents us; it will be possible to touch on only a few of the questions with which he attempts to deal. Before so doing



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a word must be said about the technique em- ployed by Prof. Graber. As he informs us, and as is quite evident from his twelve large colored plates, his results were largely ob- tained from germ bands isolated from the yolk, stained in toto with carmine, and
mounted in some resinous medium. His
first plate shows that he has also examined Lina embryos unstained and in ^itu on the yolk. Now both of these methods, though
useful for some purposes, are
quite inade-
quate to decide any delicate question con- cerning surface relief, and have consequently been all but abandoned by some recentworkers In point of detail Prof. Graber's surface views of Lina cannot stand comparison with some of the figures of insect embryos pub- lished decades ago, while nowhere is the in. adequacy of his isolation method better
shown than when he attempts to elucidate the structure of the brain. When repre-
sented at all in his figures this important or- gan is incorrectly represented. In order, therefore, properly to appreciate Prof. Gra- ber's observations it is necessary to bear in mind that his technique is somewhat defective. In the 15 quarto pages devoted to the ner- vous system there are many new and inter- esting facts, but we miss a careful treatment of the very earliest stages in the formation of the ganglia, both cephalic and ventral. It is safe to say that a few good sections through the nerve-cord of a sufficiently young Stenobothrus embryo would have brought
out some interesting facts on the formation of the median and lateral cords-facts which would have induced the author to view the nervous system of the Coleoptera in a little different light.
A short time ago Prof. Graber devoted a
paper to the important subject of metameric segmentation in insects. According to the observations therein recorded, the first seg- ments to make their appearance in the em- bryo are not the definitive body-segments (microsomites), but segments nearly or quite corresponding to the imaginal aggregates of. segments (head, mouth-parts, thorax, abdo- men) ; the definitive segments being formed by a splitting up of these macrosomites. Al- though it occurred to Prof. Graber at the time that this phenomenon might be due to a fore- shadowing of adult structure, he chose to adopt the view that the early macrosomitic segmentation was an ancestral feature. In his present paper he devotes considerable space to this subject, bringing out quite an array of pseudo-mathematical formulae, and, notwithstanding Heider's very sensible con>- ments on his former paper, still persists in seeing some mysterious palingenetic trait in macrosomitic segmentation instead of an
anticipation of the ultimate adult structure. That the latter is the correct explanation is shown by a study of Xiphidium. In this
Locustid the definitive segments make their appearance in a wave which runs from the anterior to the posterior end of the germ- band. When the whole postoral portion of the germ-band has thus been split up into about eight segments, the remainder of the definitive segments are successively intercal- ated just in front of the caudal plate. Then, and not till then, does macrosomitic segmen- tation set in. Although this method of
growth by intercalation of segments in front of the anal plate has been repeatedly shown to be the typical method in Annelids, Crus- tacea, Peripatus, Arachnids, Myriopods and, to a certain extent, in Hydrophilus (Heider), Prof. Graber maintains that it does not occur in insects. Strangely enough the very fig- ures of Stenobothrus to which he appeals, prove the very opposite of his contention, for they show quite clearly that the youngest segment must lie just in front of the anal plate. The first indications of segmentation have probably escaped Prof. Graber,-it
being impossible, as we have found after repeated trials, to detect them in semi-trans- parent, isolated germ-bands.
Prof. Graber divides insect embryos into microblastic and macroblastic, or long and short ones. Stenobothrus is microblastic;



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Lina macroblastic.
Apart from its being un-
scientific to classify things as big and little, it is difficult to understand how such a classi- fication can be of any service whatsoever. There is a complete gradation between long and short germ-bands : in Stenobothrus the germ-band is very small when first outlined on the yolk; in Mantis and Oecanthus it is somewhat larger; in Gryllus still larger; in Blatta it is nearly as long as the egg; in other forms, like Musca and the Coleoptera, it is longer than the egg. But this is not a difference in the germ-Sands, it is a difference in the amount of yolk. Stenobothrus has a direct development, Musca undergoes a pro- found postembryonic metamorphosis ; the
former needs a great deal of yolk because its embryonic developn~ent is long and compli- cated, the latter but relatively little yolk, be- cause its embryonic development is very
short and comparatively simple. Although Prof. Graber was awareof the existence of transitional forms between his long and short germ-bands, it seems never to have occurred to him while writinq the ten long quarto pages, which he devotes to this and similar distinctions. that the true differences lie in the quantities of yolk with which different eggs are provided. This is a strange omis- sion for an embryologist to make after all that has been said and written on the effects of yolk on development. Verum o$eyz' long0 fas est obrefere so?n?mm.
Equally artificial and useless is Prof. Gra- ber's division of germ-bands into straight and crooked (tanyblastic and ankyloblastic). It is obvious that the curvature of a germ- band depends on the character of the yolk surface on which it happens to lie. Thus the germ-band of a spherical egg is necessarily curved (Phryganeidae), while the germ-band on the long side of an elongate, oval egg will be more or less straight (Blattidae). It is somewhat disappointing to find that no at- tention is devoted to the important relations of the germ band to the micropylar axis, a subject on which Hallez has published two suggestive little papers (Comptes rendus, v. 101, 1885 and v. 103, 1886).
Prof. Graber finds the abdomen of the em- bryo insect to consist ofeleven true segments. He believes that he has found distinct traces of coelomic cavities in the last (eleventh) segment, and figures them in Mantis and
Hydrophilus. If correct, this observation is of great interest, since Haase has recently maintained, after an exhaustive study of the facts of larval and imaginal structure, that there are only ten segments in the insect ab- domen, the "afterstuck" not being a true segment.
The antennae are shown by Prof. Graber
to be decidedly postoral in their origin. Reichenbach pointed out that of the two
pairs of antennae in Astacus the first arises on a level with the mouth, while the second is postoral. As far as their relation to the mouth is concerned, therefore, the anten- nae of insects would correspond to the
second pair of antennae in Crustacea. The labrum arises, as Prof. Graber points out, from a pair of appendage-like organs. The honey-bee is cited as an exception to this general rule, the labrum of this species having been described as an unpairedappen- dage from the first. But CarriGi-e has re- cently shown that the labrum of the wall- bee (Chdicodoma muraria) arises as a
pair of papillae at first separated at their bases, but subsequently uniting to form a single piece. Prof. Graber has not succeeded in throwing any new light on the obscure question as to whether the labruin represents a pair of true appendages serially homolo- gous with the antennae, mouth-parts, legs, etc.
A lengthy chapter is devoted to a consid- eration of the abdominal appendages of
insect embryos. Among the numerous facts recorded the most valuable are those relating to Hylotoma berberz'dis. In this Tenthre- dinid the German investigator succeeds in es- tablishing dh ect continuity between the em- bryonic abdominal appendages and the pro-



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July 1891.1 " PSYCHE. 115
legs of the caterpillar-like larva. He finds that during embryonic life each of the eleven abdomidal segments presents a pair of appen- dages. Those on the 1st and 7th-9th segments soon disappear, while those on the remaining segments persist as the prolegs of the larva. The pair ofappendages on the tenth segment, which are at the time of their origin in line (homostichous) with the appendages of the preceding segments, move pleurad, and thus become ectostichous. On the 11th seg- ment the appendages ("afterspitzchen") are close together (entostichous). It is this last pair of appendages which corresponds to the anal legs of Lepidoptera, since, in the true caterpillars, according to Prof. Graber, the anal legs do not belong, as Haase and other investigators aver, to the tenth, but to the eleventh abdominal segment. Prof. Graber's figures are certainly far from being conclu- sive on this point. The peculiar cerci of Lyda belong to the tenth segment and are not therefore homologous with the anal legs of Lepidopterous larvae.
It is also interesting to note that the forma- tion of the embryonic envelopes and the
manner in which the dorsal body-wall is com- . pleted in the embryo Hylotoma strikingly resemble what is observed in Lepidoptera. This fact may prove to be of use as further evidence of a common ancestry for the Lepi- doptera and Hymenoptera. The embryology
of Hylotoma certainly appears to bear out the conclusion long since drawn from the adult structure of the Phytophaga, viz. : that this group is the most primitive among existing Hymenoptera. When we pass from a Tenth-
redinid to an Apid it appears that the embry- onic envelopes show a tendency to become aborted, just as they do in the Diptera, in passing from an old form like Chironomus to a recent form like Musca. The general valid- ity of this remark is in no wise impaired by the difference in the kinds'of abortive change undergone by the envelopes in the two orders. W. M. WHEELER.
BLOW-FLY.
Roffredi, M. Mkmoire sur la trompe du
cousin et sur celle du taon dans lequel on a donne une description nouvelle du plusieurs de leur parties. Avec des remarques sur leur usage, principalement pour la succion. Misc. Taurinensia, tom. iv. Turin, 1776-79.
Erichson, Wilhelm Ferdinand. En tomo-
graphien ; untersuchungen in dem gebiete der entomologie. I. Ueber zoologische
charactere der insecten, arachniden und crus- taceen. Berlin, 1840.
Brullc?, [A].
Recherches sur les transfor-
mations des appendices dans les articulhs. Ann. sc. nat., s6r. iii, tom. i, zool., 1844. Blanchard, E. De la composition de la
bouche dans les insectes de l'ordre des dip- teres. Compt.-rend., tom. xxxi, pp. 424-27, 1850, Paris.
Gerstfeldt, G.
Ueber die mundtheile der
saugenden insecten. 8O, Dorpat, 1853.
Hunt, [GI.
The proboscis of the blow-fly.
Quart. journ. microsc. sc., vol. iv., 1856, London.
Mayer, [F. J .C.]. Ueber ein neu entdecktes organ bei den dipteren. Verhandl. naturh. ver. preuss. Rheinl. und Westfalen; sitz- ungsberichte, bd. xvi, p. 106. Bonn, 1859. Suffolk, W. T, On the proboscis of the
blow-fly, Month. microsc, journ., vol. ix, I 869.
Lowne, B. T. On the proboscis of the
blow-fly. Journ. Qekett micr. club, vol. i, p. 126, 1868.
Lowne, B. T. Further remarks on the
proboscis of the blow-fly. Journ. Quekett micr. club, vol. i, p. 190, 1868.
Anthony. The suctional organs of the
blow-fly. Month. micros. journ., vol. ix, 1869.
Lowne, B. T. The anatomy and physi-
ology of the blow-fly. So, London, 1870. Graber, V. Ueber den schlundmechanis-
mus der arthropoden.
Amtl. ber. d. 50 ver-




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