EMBRYOLOGY. 
137 
Ussow’s paper on the development of the Cephalopoda [Zool. Rec. xi.- 
p. 132] is translated in Ann. N. H. (4) xv. pp. 97-113, 209-221, & 317- 
320. 
E. Ray Lankester makes some observations on the development of 
the Cephalopoda^ concerning the ovum within the ovary ; the first 
appearance of the pen-sac in Loligo, and of a similar but later evanes- 
cent pit in Octopus and Argonauta [see Zool. Rec. xi. p. 117] ; the first 
appearance of the alimentary canal as two tubes, one coming from the 
mouth and the other from the ab-oral face of the embryo, finally meet- 
ing ; the origin of the blood-vessels and lymph- spaces from the meso- 
blast ; the development of the eye, that of Nautilus corresponding to 
the embryonic state of the eye of the Dihranchiata ; finally, on the 
white bo(hes, which the author regards as atrophied or suppressed nerve- 
ganglia, nourishing the optic ganglion by their material. Q. J . Micr. 
Sci. (2) XV. pp. 37-47, pis. iv. & v. 
The development of the Pteropoda is the object of a paper by H. 
Fol, in 0. R. Ixxx. p. 196, et seg., abstract in Ann. N. H. (4) xv. pp. 439- 
441 ; the segmentation of the yelk in the shell-bearing Pteropods differs 
little from the recognized types in the Gasteropoda^ and leads to the 
formation of a nutritive portion, composed of three large spheres, and 
of a formative moiety of transparent spherules ; the embryology of the 
naked Pteropods forms a transition between that above mentioned and 
that of the Heteropods, between the formation of embryonic lamellae by 
envelopment and that by invagination. The digestive cavity is formed 
by a simple differentiation of the mass of the nutritive or central cells. 
The foot has its origin in a thickening of the ectoderm on the vbntral 
surface of the embryo, dividing afterwards into one median and two 
lateral lobes, the latter being the fins. The kidney is formed at the ex- 
pense of the ectoderm, the heart by the differentiation of a mass of cells 
in the mesoderm. The larvae have two contractile sinuses, which send 
from one to the other the liquid contained in the cavity of the body ; 
neither of them can be compared to those of the embryo of Limax. 
The appearance of the shell is preceded by an invagination of the ecto- 
derm a little in front of the ab-oral pole ; it may be compared with the 
conchylian invagination of the Mollusks with internal shells, observed by 
E. Ray Lankester, and by the author himself. 
The same author, from fresh observations made on the Pteropods Creseis 
and Stgliola, and on the Heteropod Atlanta, confirms Yan Beneden’s 
theory that the testis takes its origin from a proliferation of the ecto- 
derm in the anal region ; the ovary, on the contrary, from the inner wall 
of the intestinal tract. Arch. sci. nat. 1875, pp. 104-111, abstract in 
Ann. N. H. (4) xvi. pp. 157-162. 
The same author has also studied the development of the Heteropoda : 
the nutritive side of the blastosphere enters into the other, and the aper- 
ture of the invagination, narrowing afterwards, is the primitive mouth ; 
cells at the opposite pole give origin to the cerebroid ganglia, tentacles, 
and eyes, and this stage may be named neurula. The primitive mouth 
soon penetrates into the interior of the embryo, but does not close up or 
become the anus of the developed animal. There is also a preconchy lian 
