6 A. J. GOLDFARB. 



old; experiment 9, when 25 hours old; experiment 12, when 50 

 hours old. In Hipponoe, the eggs fused when 23 hours old, and 

 42 hours in experiment 14. In Arbacia when 48 hours, experi- 

 ment 17; 63 hours, experiment 20; 65 hours, experiment 19, etc. 

 The explanation for this wide range in the onset of fusion within 

 the same species, lies in the correspondingly wide diversity in 

 the physiologic condition of the eggs of different females at the 

 time of liberation, and hence correspondingly wide difference in 

 the rate of deterioration. 



ABNORMAL CLEAVAGE. 



Besides agglutination and fusion, there were other evidences of 

 late aging, which might conveniently be grouped together under 

 the term abnormal cleavage. Such abnormality included an 

 increasing irregularity of shape and size of the blastomeres, an 

 increasing lack of cohesion of the blastomeres, increasing retarda- 

 tion of mitosis, increasing numbers of atypic blastulse, gastrulse 

 and larvae, and an increasing inhibition of development. 



These symptoms of extreme physiologic deterioration occurred 

 essentially alike in all three species. 



The onset of abnormality in cleavage occurred at widely 

 varying ages, due to correspondingly wide variation in the phys- 

 iologic condition of the eggs at liberation. For example, in 

 experiment 4, the eggs of one female first showed marked ir- 

 regular cleavage when 2% hours old, another female when 5 

 hours old, others when 8^ hours old, etc. 



After a long initial period, during which cleavage was regular, 

 there was with further and extreme deterioration a progressive 

 increase in the degree of irregularity and in the numbers of 

 irregularly cleaving eggs. For example, in experiment 2, some 

 of the eggs of females 2 and 3 became decidedly irregular, 

 when 99 minutes old. From this time on, the number increased 

 continuously until the eggs were 214 minutes old. Beyond this 

 age, it was increasingly difficult to ascertain the ratio of irregular 

 to the M'hole number of eggs because of increasing cytolysis and 

 fragmentation of both unfertilized and fertilized eggs. In 

 experiment 16, when the eggs were i^ hours old, the average 

 number of irregularly cleaving eggs of the 3 females was 7 per 



