308 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
state of the different systems, and also of the amnion and umbilical cord, 
are described. Finally, the author notes the abundant occurrence of 
cells which, instead of definitely contoured nuclei, contained small, 
spherical, isolated granules. 
Structure of the Placenta in Man and Monkeys.* — Prof. W. Wal- 
deyer recurs to two previous communications on the structure of the 
placenta in Homo and in the catarrhine monkey Inuus nemesirinus. To his 
first question, whether the intervillous spaces normally contain maternal 
blood, he gives an emphatically afiinnative answer. He passes to the 
relation of uterine blood-vessels to the placenta, distinguishing the 
arteries and veins. The thiid part of his paj)er deals with the epi- 
thelium of the villi and the lining of the intervillous and other spaces. 
Ten opinions about the epithelium and five in regard to spaces are 
chronicled, and the paper, which is in great part a historical critique, 
closes with a brief reference to the origin of the decidua and the relation 
of the placenta of Inims to that of Homo. 
Development of Platydactylus.| — Dr. L. Will has had the oppor- 
tunity of studying the development of Platydactylus mauritianus. He 
finds that the process of gastrulation is much more primitive than in 
any Eeptile hitherto examined, while the great extent of the archenteron 
allies it to Amphibia. The difierences observed may be explained by 
the different relations of the yolk. A comparison of the Gecko-gastrula 
with that of Urodeles shows that the blastopore of Reptiles corresponds 
to the whole blastopore of Amphibia. It has hitherto been largely a 
matter of hypothesis to say that the primitive groove is formed by the 
lips of the blastopore, but the Gecko has proved the point. It can now 
also be shown that the cephalic process of the primitive stripe in other 
Amniota is nothing more than the solid arch enteric invagination of the 
Gecko. In other points, the study of the development of the Gecko 
leads to the same general results as those to which Van Beneden has 
been lately brought by a study of the development of the Chiroptera. 
Amphibian Blastopore.^ — Mr. T. H. Morgan has studied the embryos 
of Bufo lentigmosus, Rana halecina, and Amblystoma punctatum. In the 
last of these it seems that the blastopore was situated in the posterior 
part of the medullary groove, and partially surrounded by a continuation 
of its walls on each side ; that it was then overarched in its anterior 
part by a continuation of the medullary folds ; that, on account of its 
elongation, its posterior end escaped this closing over ; and that by the 
shutting in of the medullary folds the digestive tract came to com- 
municate with the neural tube by the anterior end of the blastopore, and 
with the exterior by the posterior end of the blastopore. 
This Amphibian appears to present us with an idea of the changes 
which have in general taken place in the phytogeny of the blastopore. 
The author is forced to believe that the neurenteric canal is a rudi- 
mentary organ which at some time had an important function ; it has 
remained partly stable in position, though the anus has wandered far 
from its original station. It is very probable that the neural tube once 
* Arch. f. Mikr. Anat., xxxv. (1890) pp. 1-51 (2 pis.). 
t SB. K. Preuss. Akad. Wiss. Berlin, 1889, pp. 1121-8. 
I Studies from Biol. Lab. John Hopkins Univ., iv. (1890) pp. 355-77 (3 pis.). 
