396 A. J. GOLDFARB. 



In experiment 3 (Table IV.), when the Toxopneiistes germ cells 

 were both 8 hours old, 29 per cent, of the eggs cleaved; when 12 

 hours old o per cent, cleaved. When the sperm were 10 hours 

 old, they were tested by fresh eggs, 10 minutes old, and gave an 

 average cleavage of 10 per cent. This might suggest that the 

 rate of deterioration in synchronously aging sperm cells was 

 conditioned by the rate of deterioration of the sperm. 



In experiment 5, lo-hour-old eggs fertilized by lO-hour-old 

 sperm averaged I per cent, cleavage. When the sperm was tested 

 by fresh eggs, the cleavage rose to 25 per cent. 



Similarly in experiment 6, n-hour old germ cells averaged but 

 5 per cent, cleavage; the old sperm by fresh eggs gave 91 per 

 cent, cleavage. On the other hand, in experiment 7, n -hour-old 

 germ cells gave o per cent, cleavage, in both crosses. 



The explanation for these apparently contradictory data is 

 found in a triple comparison, namely, 



1. Crossing of synchronously aged germ cells. 



2. Crossing of aged eggs by fresh sperm. 



3. Crossing of fresh eggs by aging sperm. 



If this be done it becomes apparent at once that the results 

 are due in largest part to the condition of the egg, subject only to 

 the ability of the sperm no matter how deteriorated to penetrate 

 the cortical layer and initiate development. 



In experiment 5, Table IV., lo-hour-old germ cells gave 

 I per cent, average cleavage. When the eggs io}/2 hours old 

 were fertilized by moderately fresh sperm, 45 per cent, cleaved; 

 the reciprocal cross, viz,, fresh eggs by the old sperm, caused only 

 25 per cent, to cleave. When these fresh eggs were tested by 

 fresh sperm, 28 per cent, cleaved, i. e., approximately the same 

 cleavage as when fertilized by lo-hour-old sperm. Hence low 

 cleavage in experiment a was due to the sperm, while in c and d 

 it was due to the eggs. 



In experiment 6, similar results were obtained. Eleven- 

 hour-old germ cells gave 5 per cent, cleavage. Fresh eggs used 

 to test the old sperm gave QI per cent, cleavage. But when these 

 fresh eggs were tested by fresh sperm, approximately the same 

 percentage cleaved as when fertilized by stale sperm. 



Experiment 7 is interesting because the fresh eggs used were in 



