404 BULLETIN OF THE 



out, apparently from the germinative vesicle, and it agrees very closely 

 in appearance with the germinative dot. It is the polar globule. The 

 vesicle appears to sink back into the yolk. In Cephalobus (Anguillula) 

 the germinative vesicle probably spreads out its substance either in or on 

 the clear protoplasm which at this time forms the outer layer of the 

 yolk. Hereby, it is presumable, the nuclear substance subsequently ac- 

 quires a closer relation to the spermatozoon still attached to the surface 

 of the yolk. After the polar globules appear, they are often shoved toward 

 the vaginal or smaller pole of the egg. 



The eggs of Cucullanus are of the greatest interest. Biitschli here 

 makes the discovery of a peculiar spindle-shaped body, which he at once 

 homologizes with the ''semen capsule" of Infusoria, — a structure arising 

 from the so-called nucleolus. It is hard to say what structure in the fe- 

 cundated e^g is homologous with this infusorian nucleolus; he conjectures, 

 however, that it is the germinative dot^ and that consequently it is the 

 latter which gives rise to this remarkable structure. In place of the no 

 longer visible germinative vesicle there lies in the yolk, says Biitschli, an 

 elongated, portly, spindle-shaped body of exceedingly interesting constitu- 

 tion. It is two thirds as long as the diameter of the yolk. Its middle is 

 swollen, and its ends are drawn out into fine points. Its mass is darker 

 than the yolk, tolerably homogeneous, often somewhat brilliant, and dis- 

 tinctly and finely fibrous lengthwise. Each of the fibres merges at the 

 sw^ollen middle part into a thick, dark, lustrous portion, which discloses a 

 composition out of serially arranged granules. This spindle is ejected 

 from the yolk, on the surface of which it is seen to lie. But what be- 

 comes of it he is unable to say. From a comparison with the polar glob- 

 ules of the snail's eggs,* Biitschli conjectures that the two structures 

 (spindle and polar globules) are identical, and that the dark granules and 

 fibres in both cases correspond, although no intermediate stage between 

 the two was discovered. 



Concerning the origin of the new.nuclei of the first segmentation sphere, 

 Biitschli is able to confirm in part Auerbach's observations, but also to 

 add observations not directly reconcilable with his theories. The nuclei 

 arise in the clear protoplasm of the periphery of the egg, which is accu- 

 mulated at certain points. It is not to be concluded that the nucleus 

 is the result of the metamorphosis of the protoplasm itself, it is formed 

 rather from the material of the germinative vesicle. In Cephalobus rigi- 



* These appear in the form of two more or less spheiical bodies, connected by a 

 stalk, and containing each a disk of granules, the individual grains of each disk being 

 joined to the correspondingly situated grains ©f the other by pale delicate filaments. 



