DEPARTMENT OF MARINE BIOLOGY. 205 



Experi^netital Studies upon Stale Germinal Products, hy A. J. Goldfarb. 



Ripe eggs and sperm when removed from the bodies of the sea-urchin 

 Toxopneustes variegatus undergo changes the nature of which I sought to 

 ascertain. To reduce the number of variables, all eggs and all sperm were 

 made in standardized suspensions, all products from a given individual were 

 kept separate, and the temperature, density, surface, and volume of the sea- 

 water were constant. 



(1) In the first place, it was found that fresh suspensions of the sperm from 

 different individuals varied remarkably in their power of fertilizing the eggs 

 from a given female, though morphologically the different sperm suspensions 

 were indistinguishable. The range of variability extended from 100 to 

 per cent of fertilization. 



(2) A fresh suspension of tested sperm gave widely different results with 

 different females, though their eggs were otherwise indistinguishable. They 

 varied from 100 to 20 per cent of fertilizations. 



(3) Low or high degree of fertilizability is specific for a given male or a given 

 female. 



(4) Only by experiment may we ascertain which eggs and which sperm will 

 give optimum results. 



B. 



Tested eggs and sperm removed from the body and kept at the temperature 

 of the laboratory, or slightly below this temperature, show definite changes 

 with increasing time-intervals, namely, in the reaction-time of fertilization 

 membrane formation, in the changes of the membrane itself, in the rate of 

 cleavage, in the character of the cleavage, and in the structure of the larvae. 

 In the first place, the longevity of eggs from different individuals was ascer- 

 tained and also the longevity of concentrated suspensions of sperm, as deter- 

 mined by the power of fertilizing or being fertilized. Freshly prepared and 

 tested eggs when fertilized by freshly prepared and tested sperm served as 

 controls. Stale eggs, i. e., eggs after increasing intervals subsequent to their 

 removal from the body, were fertilized by correspondingly stale sperm, until 

 the limits of fertility were reached. In a third series of experiments increasingly 

 stale eggs were fertilized by freshly prepared sperm suspensions, and lastly, 

 fresh eggs were fertilized by increasingly stale sperm. 



(1) It was found that increasingly stale eggs of a given female, though fer- 

 tiUzed by freshly prepared sperm suspensions at each trial, gave a decreasing 

 number of fertilizations, and that this decrease was approximately the same 

 for all females. 



(2) With increasing staleness of the egg, the rate of fertilization membrane 

 formation is at first progressively decreased, then sharply increased. The time 

 at which this sharp change occurs is significant. 



(3) The fertihzation membrane is increasingly gelatinized. 



(4) The permeability of this membrane is markedly altered. 



(5) The rate of cleavage is progressively retarded. 



(6) The number that cleave irregularly is increased. 



(7) The number of atypic larvae is correspondingly increased. 



When increasingly stale and tested sperm were used to fertilize freshly 

 prepared and tested eggs, their development was quite normal. None of the 

 changes just enumerated took place, showing that the deleterious factors 

 sjonptomized by these changes are potent or present in the eggs exclusively. 

 This is surprising in view of the apparent lower metabolism of the latter. 



