1897.] Embryology. 641 
Thus innumerable granules are formed and dissolved, few keeping 
intact to form the next generation. One result of the great manufact- 
ure of granules is, the author conceives, the formation of yolk in the 
egg. 
The yolk begins to appear when the egg is only 300» in diameter and 
grows to be the large mass of crystal-like bodies familiar in the eggs of 
Amphibia, The first perceived change in the egg protoplasm is the 
occurrence of minute areas near the cell periphery ; areas which include 
a considerable number of the spaces of the plastin network and become 
recognizable from the rest of the network by a difference in refraction, 
looking as if the spaces of the net were filled in by solid albumen. 
Such changed areas ultimately fuse together to form a zone in periph- 
eral part of the egg and as the yolk increases this zone extends in toward 
the nucleus, more and more. In one of the small ayeas there appear 
exceedingly minute granules along the lines of the net—these are the 
young yolk granules that enlarge as if small crystals growing in a solu- 
tion. This solution is thought to be furnished by the combined activity 
of nucleus and egg protoplasm; the nucleus furnishing paranucleic 
acid and the egg protoplasms the globulins ; these combining make para- 
nuclein and then vitilline—the yolk granule. The generations of 
figures in the nucleus form granules of nuclein that dissolve and by 
hydrolosis the nucleic acid is set free—this becomes the paranucleic acid 
that is supposed to soak out through the cell to the region where yolk is 
to form. However this may be, the granules of yolk enlarge and appear 
scattered in stout strands or cords of protoplasm that run amongst vacu- 
lues or water aes in the eee. i Hitherto tuae have been no vacules 
in the egg and the author denies tha to the 
foam-structure of Büschli ; the vacules that naw appear aroha thinks, 
due to the absorbtion of waer by the globulins. The vacules may be- 
come large and be subdivided by strands of protoplasm going across 
them. The water thus collected is later seen in deeper parts of the egg 
towards the nucleus and the egg thus takes on a spongy structure as 
the yolk develops. The minute yolk granules move centrally from this 
first place of origins in the strands amidst the vacules and now get into 
the spongy protoplasm; here each one may get into a watery vacule 
and grow to its definition size and form. The yolk granules thus start in 
the plastic net and end in a vacule; how this change is brought about 
is not evident from the author’s account. 
The interesting introductory statement and the author's views upon 
the centrosome question cannot be reviewed here as they do not bear 
directly upon the present subject. 
