604 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
Scyllium there is now yolk in the gut. But in the emulsion therein 
contained numerous nuclear structures are seen, and a comparison of 
sections shows that the merocytes gorge themselves with yolk and 
thereafter break up in the gut. “ All stages, from the condition of 
merocytes of the merocytic layer filled with yolk, to that where after 
proliferation from their place of origin they have fallen to pieces in the 
gut and sacrificed themselves for the good of the embryo, can be made 
out in one or two favourable sections. And ‘ the self-sacrifice of the 
merocytes ’ can be established, not in one embryo, but in all embryos 
between 9 mm, and 16 mm. or more.” 
Disappearance of Transient Nervous System in Elasmobranchs.* — 
Dr. J. Beard finds that in those forms of Baja or Scyllium , in which the 
development takes place in the sea, there is a considerable transient 
nervous apparatus of 600 or more ganglion-cells, while in three forms 
with uterine development this transient apparatus disappears. Thus, in 
Acanthias some 50 ganglion- cells may be developed, in Mustelus vulgaris 
there are 12 or fewer, in Torpedo not one can be seen. The difficulty 
suggested by the differences in these last three cases may be explained, 
the author suggests, by the fact that Acanthias has a fairly developed 
egg-case, while Mustelus vulgaris has an egg-case of extreme thinness, 
and Torpedo has none at all. 
~ Gastrulation of Amia calva.f — Herr J. Sobotta gives a short account 
of this process. Towards the end of segmentation the upper hemisphere 
of the egg consists of numerous small cells, extending with gradual 
increase of size to near the middle of the egg, and resting on the brown 
yolk, which is divided into a number of parts. Suddenly, however, the 
blastoderm becomes spread out like a flat cap upon the yolk. There 
is no trace of segmentation-cavity. The next step is a differentiation of 
the blastoderm into two layers coalescing at the equator. There, in a 
short time, the dorsal blastopore-lip appears, three layers are distinct, 
and the archenteron begins to be formed. When the egg is about two- 
thirds surrounded, the ventral blastopore-lip, also three-layered, appears. 
When the archenteron ^first appears, the mesoderm of the dorsal lip is 
continuous with that of the ventral lip, but by stretching the continuity 
is broken. When the egg is about four-fifths surrounded, the first rudi- 
ment of the embryo appears at the dorsal blastopore-lip. The portion 
of the archenteron associated with the ventral blastopore-lip atrophies ; 
the dorsal part is directly modified into the permanent gut. In the 
later stages the yolk shows distinct cells. 
Development of the Spiral Intestine in Pristiurus.J — Prof. J. 
Biickert begins his discussion of this problem by pointing out that 
there are two processes to be distinguished. One is the groove-like 
invagination of the endodermic tube, which results in the formation of 
a longitudinal fold. The other is a twisting of the endodermic tube on 
its long axis within its peritoneal sheath in a right-handed spiral. This 
is regarded as a natural result of the longitudinal growth of a tube 
fixed at each end. It differs from the winding of the small intestine in 
* Anat. Anzeig., xii. (1896) pp. 371-4. 
+ Yerh. Anat. Ges. X. Anat. Anzeig. Erg.-Heft, xii. (1896) pp. 108-11 (6 figs.). 
t Tom. cit., pp. 145-50. 
