1883. ] Physiology. 99 
of the ye/k hypoblast (a thick structureless membrane with 
scattered proliferating nuclei embedded in it), the blood cells are 
directly budded off and pumped up by the heart into the circulation. 
This yelk hypoblast enters into the formation of no structures 
which can be discovered except blood cells. It is, in fact, the ap- 
paratus by which the yelk is broken down into*corpuscles, and 
cannot enter into the development of the intestine, liver, pancreas, 
segmental organs or other viscera, as these have, at the stage Iam 
discussing, already appeared. The only office it therefore has is a 
yelk-elaborating function, the yelk substance being incorporated 
into the body of the nascent fish by the ordinary metabolic pro- 
cesses of growth; the circulation only functionating, as the carrier 
of the material, the yelk hypoblast is therefore also an evanescent 
structure. These facts I have mainly observed in living material, 
afterwards studying the yelk hypoblast more carefully in sections. 
Kupffer and Gensch have noticed similar phenomena in teleosts, 
but have not apparently had the good fortune to witness the actual 
process of germination of the colorless primitive blood cells in the 
living embryo, as has been done by the writer. As might have 
been anticipated these early blood cells are colorless. This is in ac- 
cord with what has been noted in the development of the blood 
of vertebrates much higher in the scale of organization. No 
writer on development, as far as I can discover, has hitherto re- 
corded the fact that he has observed this communication of the 
heart with the segmentation cavity, such as may be seen in the 
just-hatched embryos of Alosa.—F. A. Ryder. 
SENSE oF Coror IN CEPHALOPODA.—C. Keller brings forward 
evidence, states the Journal of the Royal Microscopical Society, 
that the cuttle-fish manifests in a high degree the power of adapt- 
ing the color of their skin to that of the environment. He was 
able to observe this adaptation of color in Eledone. In the Naples 
aquarium, a specimen of this octopod was under the necessity of 
escaping from a powerful lobster; during its flight, it appeared 
pale red; but subsequently, resting on a tuft of yellow rock cov- 
ered with brown spots, resembled. it so closely that it became 
almost invisible to the observer. In this case the conditions were 
decidedly very favorable for the occurrence, for yellow and dark- 
brown color cells occur in Eledone in large numbers. It should 
be added that the eye of the cuttle-fish shows an unusually high 
development. 
PuystoLocicat News.—Professor Wagener contributes? his re- 
Searches upon the origin of the transverse striæ of muscles.- 
Professor Lieberkuhn gives a notice of the results of his studies of 
e germinal layers in the mammals, especially the mole and 
the porpoise (Meerschwein). The yelk-cells enter into the struc- 
cure of the ectoderm, as well as of the endoderm.——Dr. Strahl 
‘Proc. Soc. Promotion of Natural Sciences, Merburg. 
