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REPORT ON ZOOLOGY, MDCCCXLII: 
belong to the primitive part of the serous fold : 7. The mucous fold and 
the intestines are formed from the primitive part towards the yolh, so that 
they pass from the form of a semi-canal to that of a canal ; 8. The mouth 
penetrates the ganglion chain and the primitive part, as the parts of the 
mouth originate from the latter : 9. The anus has its place in the yolk 
part, or between it and the primitive part : 10. The liver springs from 
the intestines ; the other glands originate by themselves. The heart is 
situate on the yolk side, between the serous and the mucous fold. The 
development of articulated animals is thus not so ditferent from that of 
the vertebrated animals as has hitherto been supposed, but agrees in 
important parts. The author assents to the view first taken by Rathke 
and Geoffrey St. Hilaire, according to which, the abdominal side of the 
articulated animals corresponds to the dorsal side of the vertebrated; 
and adds also, that the legs of the articulated animals correspond to the 
dorsal plates of the vertebrated, which, in the former, grow to free limbs, 
in the latter, unite with those of the other side, and so form the canal 
for the spinal marrow, and only in fishes form themselves, in the dorsal 
fin, into a sort of organ of motion. The wings of insects, as above men- 
tioned, correspond, according to the author’s view, with the legs of ver- 
tebrated animals. The author considers the branchiae of the Crustacea 
as corresponding to the wings of insects ; but they are always united with 
the legs, and form themselves sometimes into organs of respiration, some- 
times into organs for steering, since, in the Crustacea and Entomostraca, 
the original form of the legs is that of the cleft feet, one arm of which 
often becomes an organ of respiration (branchia). 
If we should, as Oken has done, consider the wings of insects as 
branchiae, the comparison may be made, partly with the larvae of insects, 
partly with articulated worms. The researches and conclusions of the 
author, already ascertained by his microscopic observations in the region 
of physiology, deserve all attention ; with regard to the history of de- 
velopment in the egg, the relation in structure of the vertebrated and 
articulated animals, can be most certainly explained ; and, perhaps, the 
comparison between the two, which possesses much interest, may be 
farther conducted in a judicious manner. I must however confess, that 
I have no doubt, but that from a general comparison of the organization 
of both divisions of the animal kingdom, the conclusion must be drawn, 
that there is no actual identity of the parts of the body; but that a 
comparison can be instituted only in reference to the functions of the 
organs. So much the more important is it to compare the development 
of the egg in both. 
Steenstrup’s work, Uber den Generationswechsel oder 
die Pfortpflanzung imd entwickeliing durch abwecliselnde 
196 
