415 



egg of Bufo lentiginosus. A brief summary of the changes that take 

 place iu the egg at this time is here given; a detailed account, with 

 figures, will appear in the Journal of Morphology. 



At the end of the hibernation period, the egg is still attached to 

 the wall of the ovary. It contains a very large germinal vesicle in 

 which there are 24 chromosomes arranged iu pairs and also a large 

 number of nucleoli. Just before the breaking down of the nuclear 

 membrane (which takes place but a few hours before the egg leaves 

 the ovary), the ends of each pair of chromosomes unite to form a 

 closed ring near which a small aster appears. Very soon after this 

 stage, chromosomes and asters disappear entirely; presumably the 

 chromosomes break up into minute granules which do not have the 

 power of staining intensely and are therefore indistinguishable from 

 the granular cytoplasm. 



The nuclear membrane disappears first at the side of the nucleus 

 nearest the centre of the egg, and in this region there appears the 

 beginning of the radiation of nuclear substance that later extends 

 over a considerable part of the upper hemisphere of the egg. The 

 rays forming this radiation extend from the coarse caryoplasmic 

 network that fills the upper part of the germinal vesicle, into the 

 dense homogeneous band of cytoplasm that surrounds the lower part 

 of the nucleus. In my previous paper I have called this band of 

 cytoplasm a "line of radiation". It later forms part, if not all, of 

 the first polar spindle. 



By the time that the radiation has appeared in the lower part 

 of the germinal vesicle, all of the nucleoli have lost their power of 

 staining and have become irregular, yellowish-green, refractive bodies 

 which soon break up into small pieces that can be traced until 

 their total disappearance when the first polar body is about to be 

 given otf. All of the nucleoli are absorbed; none of them remain 

 to form the chromosomes of the first polar spindle, as believed by 

 Carnoy and LebPwUn ^) to be the case in the eggs of Triton, Rana, 

 Bombinator and Bufo vulgaris. 



It is absolutely impossible to discover any traces of chromatin 

 in the egg from the time of disappearance of the chromatin rings 

 (just before the nuclear membrane breaks down) until the line of 

 radiation has shortened into a straight or slightly curved fibrous band 

 and the radiation extending out from it in every direction has decreased 



1) Carnoy et Lebuux, La vesicule germinative et les globules 

 polaires chez les Batraciens. La Cellule, t. XVII, 1900. 



