Article beginning on page 457.
Psyche 6:457-459, 1891.

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PSYCHE.
tinctly separated from the seventh than are the other segments from each other, without hairs, but armed with two pairs of terminal hooks; the upper or anterior pair blunt
spine-like, approximated and stout at base, somewhat appressed but not terminally
recurvate or hooked; the lower or inferior pair more removed, terminally recurved
below, sharp claw-shaped, slightly divergent, directed inferiorly; anterior to the latter on ventral surface there is a pair of small tuber- cles. Ten pairs of stigmata or spiracles, as follows: Prothoracic spiracle on side at anterior margin of prothorax; mesothoracic spiracle on anterior border of wing bases; metathoracic spiracle in the anterior lateral angle of dorsum of scutellar segment; and an abdominal spiracle in the anterior lateral corner of dorsum of each of the abdominal segments I to 6, the 7th segment having a small median lateral one higher up on side of dorsum ; the spiracles (except the mesotho- racic) appear as a corneous circle marked by radiating lines within, those on the 7th segment showing this structure less dis- tinctly, while the mesothoracic spiracle is indistinct and does not usually reveal this structure at all.
Length, 8.5 mm. (including cephalic
horns) ; width of basal abdominal segments, 2.25 mm. ; length of long filament-like hairs of 3d to 5th segments about 3 mm., those of 1st and ad segments over 4 mm.
THE PRIMITIVE NUMBER OF MALPIGHIAN VESSELS IN INSECTS.-I.
Since the days of Schwammerdam
anatomists have most naturally evinced
far greater interest in the physiology
than in the morphology of the Malpig-
hian vessels. Hence we are in posses-
sion of a much larger body of facts bear- ing on the function than on the
phylogenetic history of these interesting organs. Their possible relations on
the one hand to the tracheae, which
have a somewhat similar orgin, and on
the other to vermian nephridia, which
have a similar function, are still
shrouded in the deepest obscurity.
Before these fundamental questions
can be answered satisfactorily, it will be necessary, I believe, to come to some
these is the question as to the primitive number and arrangement of the organs
under consideration.
No fact in insect development is
better authenicated than the derivation
of the Malpighian vessels. It was
Butschli* who in 1870 first showed that
in the bee the paired excretory organs
arise as hollow diverticula of the hind- gut which itself arises as a more exten- sive invagination of the ectoderm at
the caudal end of the embryo. All
succeeding writers have confirmed this-
observation.
It is worthy of note that there is ex-
tensive variation in the time at which
the vessels make their appearance in
definite conclusion in regard to several ,
* Zur entwicklungsgeschichte der biene. Zeitschr. f. minor questions. orem most among wiss. ZOO^. bd. ,s,o, p. 541.



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different insects.
In some cases, as in
the Coleoptera and Hymenoptera
(Doryphora, Chalicodoma) , they are
budded off from the hind-gut when the
latter is still very shallow and the
embryo comparatively young. In other
cases they arise late in development
after the hind-gut has reached a con-
siderable length (Orthoptera : Blatta,
Xiphidium, etc) . Notwithstanding
these variations, the derivation of the
hind-gut and its appendages from the
ectoderm is so easily ascertained that
it cannot escape even a very careless
observer.*
The few accounts concerning the
origin of the Malpighian vessels in
Myriopoda are quite definite. Accord-
ing to , Heathcotet in JuZus terrestris
a single pair of vessels is formed as
outgrowths from the hind-gut, and
Metschnikoffj: long ago made a similar
observation on S.tron.gylosoma gueri-
nil. Zograffs's figures show conclu-
sively that the Malpighian vessels of
Geophilus form no exception to the
general rule. It is, therefore, quite
certain that the Myriopoda and Hexa-
poda, which I propose to unite under
* According to Graber (Vergleichende studien, etc. Denkschr. d. k. akad. d. wiss. bd. 56, 1889, p. 25 et seq.), the hind-gut probably arises from the mesentoderm in Musca. This if true would make the Malpighian ves- sels mesentodermic. I have elsewhere pointed out (Psyche, June 1891, p. 98) what appears to me to be the true explanation of the phenomena observed by Graber. + The early development of fulus terresin's. Quart. journ. micr. sci., vol. 26, 1886, p. 461. + Embryologic der doppeltfiissigen Myriapoden. Zeitschr. f. wiss. zool. bd. 24, 1874, p. 262. $ Material k moznania embrionalnavo razvetia Geo- philus ferruginous Lk. e G. proxmius L. K. Trudi zool. mus, Moscow, 1882.
the term EUTRACHEATA, agree in the
mode of origin of the excretory organs.
These may therefore be regarded as
strictly homologous in the two groups.
Far less satisfactory are the accounts
concerning the so-called Malpighian ves- sels of other Arthropods. Among the
Crustacea (Amphipoda) two, (or in
Melita only one) tubular diverticula of
the mid-gut have been called Malpigh-
ian vessels, on account of their resem-
blance in form and function to the
excretory organs of the Eutracheata.
But there is this great difference : the Crustacean vessels are not derived from
the ectoderm but according to Spencer*
and Mme. Pereyaslawzewa,f from the
entoderm.
Peripatus, I need hardly state, has
no Malpighian vessels, the numerous
pairs of nephridia subserving the excre- tory function.
In the Arachnida a pair of branching
tubules opening into the mid-gut near
its junction with the hind-gut have been called Malpighian vessels. There are,
however, reasons for doubting their
homology with the urinary organs of
insects. Lomanj: believes that they
correspond to the mid-gut diverticula of the Arthrostraca and maintains that they do not contain urates. The accounts
of their origin in the embryo are con-
* The urinary organs of Amphipoda. Q journ. micr. sc. (2) v, 25, 1885, p. 183-190.
+ Etudes sur Ie ddveloppement des Amphipodes. I.
Le ddveloppement de Gammaruspoecilurus, Rhk. Bull. soc. imp. nat. d. Moscou, no. 2 ann6e 1888. $ Ueber die morphologische bedeutung der sogenann- ten Malpighischen getisse der . echten spinnen. Tij- dschr. nederl. dierk. 5 deel. I, 1887.




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flicting and somewhat unsatisfactory.
In the scorpion according to
Laurie*
' the vessels arise as tubular outgrowths of the mid-gut. Derivation from the
ectoderm is in this instance precluded,
since the hind-gut, or proctodaeum,
does not make its appearance till after
the Malpighian vessels have' arisen.
On the other hand Morin,? Schimke-
witch: and Locys are of the opinion
that the vessels in the Araneina are
budded off from the distal end of the
hind-gut in much the same manner as
in insects.
The only remaining possi-
bility ; viz., the derivation of the Mal- pighian vessels from the mesoderm is
advocated by Kishinouye. ]I
These wide differences in opinion
regarding the origin of the Malpighian
vessels in all Arthropods, excepting the Eutracheata, commend us in doubt-
ing the homology of the various or-
gans hitherto comprised under the
same name. In default of definite
proof of entodermic origin in the ves-
sels of Crustacea and Arachnida, the
suggestion of a new terminology would,
o? course, be premature. But even if
the organs in question should be ulti-
mately shown to be ectodermal in the
lower Arthropods, as well as in Eutra-
cheata, the few conclusions advanced
*The embryology of a scorpion (Euscorpius italicus). journ. micr. sc. vol. 31, 1890, p. 128.
-(å Zur entwicklungsgeschichte der spinnen. Biol- centralbl. bd. 6, 1887.
+ Etude sur Ie ddveloppment des araignfees. Arch. biol. tome 6, 1887.
$ Observations on the development of Agelena nevia. Bull. mus. comp. zool. vol. 12, no. 3, 1886. 11 On the development of Araneina. Journ. coll. sci. im. univ. Japan, v. 4, pt. i, 1890.
in the present paper will be in no wise
affected thereby, since I do not under-
take to establish the ancestral number
of Malpighian vessels for the Arthropoda as a class but only for the subordinate
group Hexapoda.
Both the peculiar numerical con-
stancy of the Malpighian vessels within
limited groups of Insecta, and the great numerical disparity between different
groups, could not fail to attract the at- tention of the entomotomist. Brauer,*
especially, has made use of these con-
ditions in his classification of insects as Polynephria and Oligonephria. It was
also readily seen that the Malpighian
vessels when limited in number are,
with very rare exceptions, arranged in
pairs. Hence Gegenbaurf and others
have drawn the correct inference that
the paired arrangement represents a
primitive feature. It was furthermore
observed that embryos and larvae of
polynephric forms have a much smaller
number of vessels than the correspond-
ing imagines ; the converse being very
rarely, if ever the case. When, within
more recent years, the great phylogen-
etic value of the embryonic stages was
established, it was readily surmised that the condition of the excretory organs in the embryo might furnish some clue to
their ancestral number and arrangement.
The interesting facts brought to light by the study of the embryonic excretory
system of vertebrates certainly justify
* Systematisch zoologische studien. Sitz.-ber. math. naturwiss. klasse. k. akad. wiss. 91, bd. I. abth. Wien. 188.5.
f Grundriss der vergeescheinden anatomic. 2. auflage. Leipzig, 1878, p. 292.




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us in looking for important revelations
in other descendants of annelid-like
forms. Taking the embryo as our main
guide in determining questions of
primitive number and arrangement, we
find the possible hypotheses on the
Malpighian vessels to be quite limited ; since in no insect embryo have more
than three fairs of these vessels been
found.
Gegenbaur* observed the frequent
recurrence of the number two (some
times expressed only in the common
openings of numerous vessels) through-
out all the divisions of the Arthropoda. Hence this number, he concludes, may
be regarded as primitive. It is obvious
that this statement may be correct for
the Arthropoda in general and still in
no wise conflict with the view that the
ancestor of a particular subgroup may
have had more than two Malpighian ves-
sels. Thus Protentomon may have had
several pairs and these, if ascertainable, might be regarded as constituting the
typical number for the Hexapoda.
The
remote ancestor of Protentomon may
have had but a single pair.
Two views have been advanced as to
the number of Malpighian vessels in
BRIEF NOTES.-Thorell has just published
a second octavo volume of about 500 pp. on the spiders of Indo-Malesia. It is devoted to the lower groups, and closes with a
table of the geographical distribution of the 462 spiders so far known from that region. Our students of Neuroptera will be grate- ful to Nathan Banks for his Synopsis, cata- logue and bibliography of the neuropteroid insects of temperate North America just
primitive insects.
Paul Mayer,* in his
well known treatise, expressed himself
very clearly on this subject. After
doing full justice to all the facts at his disposal he concludes: "Dass die
anzahl der paare bei Protentomon 2
betrug, 1st so gut wie sicher." The
embryological evidence accumulated in
1876 was perhaps too meagre to lead to
any other conclusion.
In two recent papers Cholodkowsky-f-
advances the opinion that the primitive
number of Malpighian vessels in insects
is two. He bases his conclusions on
some very interesting observations, to
which I shall have occasion to revert!
when I come to consider the Lepidop-
tera.
My own observations on the embryos
and larvae of several insects, together
with the facts recorded by other ob-
servers, lead me to the conclusion that
the ancestral number of Malpighian
vessels in insects was six. In other
words, Protentomon was not only
hexapodous but also hexanephric.
* Ueber ontogenie und phylogenie der insekten. Jen. zeitschr. natiirwiss. 10 bd. 1876, p. 142. t Surles vaisseaux de Malpighi chez les lepidopteres. Compt. rendus. tome 98, p. 631-633, Sur la mor phologie de l'appareil urinaire des lepidoptferes. Arch. biol. tome 6, fasc. iii, 1887.
issued in the transactions of the American entomological society. The tables are very simple and brief, perhaps erring in this latter feature.
Interesting recent papers on relationships among butterflies will be found in Spuler's Zur stammgeschichte der Papilioniden (2001. jahrb., vi, 34 pp., 2 pi.), and Haase's Ent- wurf eines naturlichen systems der Papilioni- den (Bibl. zool., heft. viii, 120 pp., 8 pi.).



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