March 25, 1910] 



SCIENCE 



465 



zona radiata by Wilson. The perivitelline space 

 arises by the extrusion of the homogeneous con- 

 tents of the alveoli of this layer through the 

 vitelline membrane into the sea water, where it 

 forms by swelling a layer of jelly, which may be. 

 as much as 100/4 in diameter. The walls of the 

 alveoli remain and form a protoplasmic lining of 

 the vitelline membrane and exceedingly delicate 

 strands of protoplasm crossing the perivitelline 

 space. The perivitelline space is, therefore, in- 

 traovular. 



The fact that the egg of Nereis thus secretes 

 its own jelly may readily be demonstrated by 

 fertilizing under the microscope with excess of 

 sperm. If excess of sperm be added to closely 

 placed eggs and a cover glass applied so as to 

 force the eggs into a single layer, and the prepara- 

 tion examined with no loss of time, the spermato- 

 zoa will be seen in large numbers in immediate 

 contact with the vitelline membrane. In one or 

 two minutes the spermatozoa are moved away 

 from the surface of the eggs by some invisible 

 repelling substance, and they unite in lines that 

 form hexagonal areas, with an egg in the center 

 of each. The substance that sweeps the sperma- 

 tozoa away from the eggs is the jelly, and syn- 

 chronously with its formation the cortical layer 

 disappears, leaving the perivitelline space crossed 

 by protoplasmic strands as already noted. 



In the case of each egg a single spermatozoon 

 remains attached to the vitelline membrane. But 

 this spermatozoon requires about twenty-five min- 

 utes to penetrate completely through the mem- 

 brane. The stimulus to development thus pre- 

 cedes penetration by a considerable interval of 

 time. 



Unfertilized eggs retain the cortical layer and 

 form no jelly, but if they are centrifuged or suffi- 

 ciently stimulated with KCl the jelly forms, the 

 perivitelline space arises and maturation takes 

 place. KCl eggs may then differentiate further, 

 but without cleavage. 



It would appear, then, that any condition that 

 so alters the permeability of the vitelline mem- 

 brane as to permit the outflow of the alveolar 

 contents of the cortical layer initiates develop- 

 ment, but that the normal continuation of devel- 

 opment is dependent on other factors. 

 Factors which Influence the Maturation of the 



Egg and Ovulation in the Domestic Gat : W. H. 



LoNGLET, Yale University. (Introduced by W. 



E. Coe.) 



The course of maturation and ovulation in cats 



which have paired has been briefly sketched by 

 E. Van der Stricht^ in a preliminary paper. He 

 finds correctly that two polar bodies are formed, 

 the first in the ovary, and the second in the Fal- 

 lopian tube, but does not note, as the case is, 

 that the formation of the second is conditioned 

 by the entrance of the sperm head into the egg. 



The conclusions herein arrived at depend largely 

 upon data derived from animals not allowed to 

 pair. 



Tube eggs before fertilization or in early phases 

 of that process, that is, just after leaving the 

 ovary, are approximate spheres. Each has a thick, 

 tolerably uniform zona with no leucocytes or 

 granulosa cells within it. The corona of each is 

 highly radiate. 



The study of the recently ruptured follicle shows 

 that its epithelial lining is always very thin and 

 the follicle just before rupture shows a high 

 cumulus containing lacunse. 



These criteria exclude from the class of normal 

 eggs all such as are found undergoing maturation 

 in the ovaries of animals sexually immature, or in 

 mature animals at the beginning of heat, or at 

 any time during heat, if pairing does not occur. 

 In so far, therefore, as it anticipates normal 

 development, the maturation of the cat's egg is 

 dependent upon pairing. 



Of ten animals killed at periods ranging from 

 23 to 50 hours after pairing, six had already ovu- 

 lated, and the one killed at 23 hours would surely 

 have done so within the longer time mentioned. 

 In a second series of five animals not allowed to 

 pair, individuals were killed at 56, 73, "4 and 

 144 hours after first being noted to be willing to 

 pair. None of these had ovulated, as opposed to 

 the 70 per cent, of the first series. Still another 

 was killed one week after the close of a period of 

 heat of at least six days. This animal likewise 

 had not ovulated. 



The ovaries of the animal last mentioned showed 

 three distinct series of degenerating eggs, which 

 would easily bear the interpretation that they 

 represented groups which had successively come 

 to the point where they awaited the stimulus of 

 pairing to bring about their discharge, but failing 

 to receive it, had degenerated. 



Thus in spite of the fact that Bonnet" has 

 recorded a tube egg in an animal which he be- 



' " Vitellogfenese dans I'ovule de la chatte," Ann. 

 de la Soc. d. Med. d. Gand., 1908. 



' " Beitrage zur Embryologie des Hundes," Anat. 

 Eefte, Bd. IX., 1897. 



