QUARTERLY CHRONICLE OF MICROSCOPICAL SCIENCE. 85 
nerve-system, the epidermis, and the epithelial lining of the 
pharynx and rectum and the tracheal tubes; a deeper 
layer which divides itself into a number of protovertebre-like 
segments, the embryological significance of which is not 
apparent. They give rise to the muscles, the body cavity 
(by splitting), and perhaps the mid-intestine. Kowalewsky 
first saw these in the Karth-worm, Metschnikoff in Scorpion, 
and later in Spiders, in Mysis, and other Crustacea. ‘They 
do not appear to have been recognised in any of the many 
Insects studied recently by embryologists, except in the 
Termites. Thirdly, the embryonal membranes of Arthro- 
pods are of great importance ; they are of two kinds, cellular 
and structureless. Metschnikoff thinks that they cannot be 
held in any way to represent one another. Insects have an 
amnion built up of cells, the best figures of which are to be 
seen in Kowalewsky’s paper, Mem. Acad. St. Petersburg, 
seventh series, vol. xvi, No. 12, I871. Crustacea have struc- 
tureless “‘ larval skins,” which are shed in the egg. Metsch- 
nikoff has found such larval skins also in Insects ; for instance, 
in Platygaster and other Pteromalina. Claparéde found 
them in Acari. In Myriapods we can only compare New- 
port’s amnion and a second structureless membrane also 
present with the larval skins of Crustacean embryos. In 
particular, the cuticular vesicle, which was found by Fritz 
Miiller in the Isopod Ligia and is held by some embryolo- 
gists to be a nauplius-skin, presents close agreement with the 
inner retort-shaped membrane of a Julus-embryo. Hence, 
again, the Myriapods separate themselves from the Insects. 
Fourthly, this assimilation in development to the Crustacea 
rather than to the Insects is more strongly confirmed than by 
any other fact, by the peculiar curvature of the embryo. In- 
stead of the primitive neural region (keim-streif) being con- 
vex outwardly and concave te the yelk—bending up round it 
at each end when seen in vertical antero-posterior-section, as 
in all Arthropods except the higher Crustacea (especially 
Amphipoda)—instead of this, all the Myriapods studied show 
the Amphipod’s position, having the neural surface concave 
by the bending over of the tail and head on this side towards 
one another. This appears to be a fact of high significance. 
Fifthly, it is remarkable that here, as a further disagree- 
ment with what occurs in Insects, and agreeing with what 
occurs in some Crustacea, e. g. Daphnoidea, we find that in the 
Myriapods the food-yelk is not enclosed within the parietes 
of the alimentary canal or its diverticula, but lies outside it 
in the body cavity between the alimentary and tegumentary 
walls. (See abstract of Bobretzky on Oniscus, above.) 
