230 



Part III — Ttventy -fifth Annual Report 



But the egg contents, being now more cohesive, withstood the pressure 

 without breaking up. 



When the egg was crushed the yolk corpuscles poured out all oscillat- 

 ing, leaving no nucleus to be seen ; there were some groups of corpuscles 

 a little larger than the others. The zona retained its shape and 

 appeared quite smooth in some, although in others it was still tuberculated, 



When the egg was squeezed sufficiently to cause some of the contents 

 to flow out, a sort of peri vitelline space began to appear, formed after the 

 escape of a quantity of yolk by the entrance of water. In the 

 partially emptied egg there were protoplasmic threads from the remaining 

 portion of yolk to the internal surface of the egg-shell, aud the zona had 

 lost its corrugations. Wilson gives a drawing of an egg that had 

 apparently lost some of its contents; in it little protoplasmic threads con- 

 necting the inside of the zona to the segmented mass left inside are indicated. 



The clear protoplasm of which the nucleus in the ripening egg consists 

 appears now in the ripe egg to have extended through the yolk, binding 

 the granular matter together, and apparently making a clear, sharp, 

 external layer to the yolk-sphere. 



When the yolk granules issued thiough pressure, they sometimes took 

 up some of the clear protoplasm, and they are seen covered with a clear 

 layer — a little entity consisting of one or many yolk corpuscles covered 

 with a clear protoplasm (fig. 41). 



Out of one egg there was pushed a clear network-like mass (fig. 7), 

 which might have been a crumpled membrane. The egg from which it 

 came was continually changing its shape. The "network " was seen free 

 in another case, away from t le egg. 



Sub-Dividing of the Unfertilizep Egg. — Some of the eggs were 

 kept overnight in a dish. By next day some of the eggs had given oft* 

 little spherical bodies of various sizes. They were formed by the outflow 

 of the egg contents through the micropyle. 



These bodies consist of a larger or smaller number of granular yolk 

 corpuscles surrounded by clear protoplasm. Sometimes they can be seen 

 attached to the egg at one point like a number of little balloons attached 

 to a large balloon. They may vary in size or may be all nearly 

 equal (fig. 16). Changes were observed to take place in these bodies, even 

 while the egg was examined. A* dark globule was added to one egg 

 as I watched. They become detached, and go off resembling in appearance 

 a little egg. Although they have a sharp outline they have no cell wall 

 (fig. 41). 



During the night the eggs had been actively budding off these little 

 spheres, so that next day it was hardly possible to treat any of the eggs 

 in the dish as normal eggs. 



Some of the eggs showed a hyaline investment, which appears to be 

 formed by the exudation of clear protoplasm from the egg. An egg 

 had a crumpled hyaline investment, which looked as if it were the outer 

 zona layer which had become loosened. 



Artificial Fertilization. — On June 3 some eggs were obtained from 

 the mass lying near the mussel. They were motionless and unsegmented. 

 Some of them showed a little refractive protoplasmic process on the out- 

 side of the zona. 



A piece of the mantle of a male mussel was put into water. The 

 water became milky, and when examined was found to be alive with 

 active sperms. 



Some of the fluid was put, by means of a pipette, into the dish contain- 

 ing the eggs. It was possible to see under the microscope the sperms 

 whirling about among the eggs. 



