A. J. GOLDFARB. 



were 95 hours old) was due to a physiologic deterioration of the 

 sperm, comparable with that in the eggs, and how much the re- 

 duction was due to an excessive mortality, as a result of which 

 there were insufficient numbers of effective sperm, was not de- 

 termined. Both factors probably play important roles, though 

 I am inclined to believe that a differential mortality plays a 

 major role. 



In the above experiment and in others, the decrease in cleavage 

 with these very old sperm was amazingly small, far less than in eggs 

 of like age. It should be noted however that the sperm in these 

 experiments were allowed to age in the "dry" or concentrated 

 condition, without the addition of sea water, and in this condition 

 their metabolism is at a minimum, hence the maximum longevity. 



In experiment 13, various types of crosses corroborate the 

 above conclusions. Eggs and sperm were fertilized at varying 

 intervals until both germ cells were 48 hours old, at which 

 time only 14 per cent, cleaved. This 48-hour-old-sperm was 

 tested with i8-hour-old eggs and with ^--hour-old eggs. The 

 1 8-hour eggs gave 98 per cent, cleavage; the ^V-hour eggs 70 per 

 cent. Samples of the same eggs were also fertilized by sperm 18 

 hours old. The 48-hour eggs gave 13 per cent, cleavage; the 

 i8-houreggs 92 per cent, and the ^-hour eggs 70 per cent. It 

 will be at once evident that the sperm at both ages gave a remark- 

 ably similar cleavage per cent, with fresh, with moderately old and 

 with old eggs, i. e., the sperm have undergone little if any physi- 

 ologic deterioration between 18 and 48 hours after liberation. 

 The 48-hour eggs gave 14 per cent, cleavage by 48-hour sperm and 

 13 per cent, with i8-hour-old sperm. The i8-hour-old eggs 

 gave 98 per cent, cleavage with 48-hour-old sperm and 92 per 

 cent, with 1 8-hour sperm. The ^-hour-old eggs gave 70 per 

 cent, cleavage with 48-hour-old sperm and the same per cent, with 

 i8-hour-old sperm. 



The cleavage was determined essentially or exclusively by the 

 condition of the eggs. 



The decrease in cleavage in the fresh eggs was due as in Toxop- 

 nenstes experiment to the poorer physiologic condition of the 

 eggs at the time of liberation. Good fresh sperm cannot cause 

 physiologically poor eggs to cleave to any greater extent than old 



