318 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
stretched to its maximum extent, and at the same time should be elastic 
against pressure tending to throw it into folds.” The change required 
would thus be the substitution of liquid contents instead of nutritive 
contents. With the absorption and retention of this liquid, under a 
certain pressure, the trophoblast is specially concerned. Moreover, the 
spacious blastocyst affords safe lodging for the developing head of the 
embryo. But the function of the trophoblast will be rendered more 
effectual if the hypoblast follows suit, and constitutes as soon as 
possible an inner lining to the trophoblast sac. By these and other 
considerations Prof. Hubrecht shows the necessity for the precocious 
segregation of part of the hypoblast in mammals. 
Nomenclature of Chicken Embryos for Teaching Purposes.* — 
Prof. W. Baldwin Spencer suggests the use of fixed and simple designa- 
tions to indicate the stages in chicken embryos, and he recommends the 
use of letters of the alphabet, such as was adopted by Prof. Balfour in 
his description of the early stages of Elasmobranch fishes. He defines 
the stages, and gives figures to explain and illustrate his meaning. 
Development of Salamandra atra.f — Prof. B. Wiedersheim has 
examined a large number of females, and while for the most part con- 
firming the observations of Schreibers, C. Th. Siebold, and Czermak, has 
found out more than one new fact of importance. In one case, instead 
of two embryos there were three; in another exceptional case there 
were four. Prof. Wiedersheim killed the animals in sublimate solution 
and cut out the gravid uteri. Yet, except in two cases perhaps abor- 
tive, the embryos remained alive, so securely closed is the distal end 
of the duct. The histology of the oviduct is described : — the numerous 
vessels between the serous and muscular layers, the plaited mucosa, the 
cilia all over the surface, the thousands of leucocytes in the inter- 
cellular spaces of the sub-mucosa and mucosa. In the uterus these spaces 
are occupied by crowds of red blood-corpuscles which burst the mucosa 
and are set free in the cavity in which the embryo lies. In this fluid, 
rich in oxygen aud in nourishment, the embryo breathes and feeds. Its 
mode of respiration is no longer an enigma. As the material furnished 
by the undeveloped ova becomes exhausted there is a more abundant 
supply of blood, lymph, and epithelial debris from the wall of the 
uterus. After birth the mucosa is renewed, a process which recalls 
similar phenomena in mammals. 
Disputed Points in Teleostean Embryology. J — Mr. J. T. Cun- 
ningham draws attention to some of the firmly established facts, and 
distinguishes the sound from the unsound in recent descriptions and 
arguments. In many ova of Teleosteans there is no element in the egg- 
cell other than the pellucid yolk and the peripheral pellicle of proto- 
plasm ; in the gurnard and mackerel there is a somewhat large globule 
of oil ; in others there are several free in the yolk or fixed in the cortical 
protoplasm. In all non-pelagic and in some pelagic ova the yolk is dis- 
continuous, consisting of many yolk-spherules. Yolk-segments, inter- 
mediate between numerous yolk-spherules and the homogeneous yolk of 
* Proc. Roy See. Victoria, 1890, pp. 23-6 (4 pis.). 
f Arch. f. Mikr. Anat., xxxvi. (1890) pp. 469-82 (1 pi.). 
+ Ann. and Mag. Nat. Hist., vii. (1891) pp. 203-21. 
