152 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
of the blastodermic vesicle, and the longer deferred is the impression 
of characters due to the physical effects of the uterine walls. 
Formation of the Decidua.* — Dr. F. Nordmann discusses some vexed 
questions, and states the results of his observations. The lower uterine 
segment belongs, so far as its musculature is concerned, to the corpus 
uteri, differing very markedly from the cervix ; it is covered by a mucous 
membrane which in its structure must be reckoned to that of the uterus, 
and, like it, shares in forming the decidua. The mucous membrane of 
the cervix takes no part in forming the decidua ; the cervix remains 
normally closed during the whole period of pregnancy. The inner 
orifice ( Muttermund ) lies where the musculature of the corpus uteri 
suddenly thins off and the unchanged mucous membrane of the cervix 
begins. 
Early Stages of the Development of the Rabbit. f — Mr. R. Assheton 
has re-investigated the early stages of the development of the Rabbit, 
on which Van Beneden published his classical observations fifteen years 
ago. He comes to the conclusion that that author’s description of 
segmentation was inaccurate ; he can find no trace either of his blasto- 
pore or of any gastrulation ; nor is he any happier with the speculations 
of Robinson concerning the existence of a hypoblastic wall to the 
blastocyst surrounded subsequently by the epiblast, for he can find no 
evidence in support of it. Rauber’s layer fuses with the inner layer 
of epiblast as described by Balfour and Heape, but this fusion has but 
slight morphological significance, as the existence and disappearance are 
caused mechanically by ontogenetic conditions. The growth round of 
the hypoblast is apparent only, being due to the presence of a zone 
of specially active epiblast surrounding the embryonic disc. 
Primitive Streak of the Rabbit.J — Mr. R. Assheton discusses the 
causes which may determine the shape of this streak and the part of 
the embryo formed by its activity. He points out that in recent years 
the theory of concrescence has been used to account for the growth 
in length of the Vertebrate embryo. No trace of such an occurrence 
can be found in the Rabbit, and the growth in length of the embryo can, 
he thinks, be much more easily accounted for by a process of addition 
of new cellular units between the pre-existing embryo and an area 
of rapid cell-production. He commences by discussing the earliest 
signs of the formation of the secondary area of proliferation, but much 
of this part of his essay would be unintelligible without constant reference 
to his figures. It may be said, however, that he finds that the secondary 
area of activity arises as a small spot placed excentrically to the primary 
centre of activity. It increases in magnitude, elongates, and becomes 
much reduced in breadth towards the centre of its length, and it is 
deeply grooved. This groove, after attaining its greatest length, rather 
suddenly disappears altogether. Instead of a groove a ridge appears 
along the median line of the area, and the area itself shortens and 
diminishes in size, but does not finally disappear until the last segment 
has been formed. The process of elongation of the primitive streak 
* Verh. Phys. Med. Ges. Wurzburg, xxviii. (1894) pp. 45-62. 
f Quart. Journ. Micr. Sci., xxxvii. (1894) pp. 113-64 (5 pis.). 
f Tom. cit., pp. 191-221 (3 pis.). 
