Variahiliiy of Eggs and S-perm of Sea-Urchins. 



83 



HIPPONOE. 



The variation in cleavage of Hipponoe eggs was essentially the same 

 as in Toxopneustes. The data are brought together in table 6. 



Samples of eggs of a given female fertilized by different males gave 

 45 and 76 per cent cleavage, respectively, a range of 31 per cent. 

 (Experiment 6/21.) 



Eggs of different females fertiUzed by the same male varied from 5 to 

 81 per cent in the 13 experiments cited in table 6. The maximal 

 difference in each experiment was 5, 9, 10, 17, 24, 47, 54 per cent and as 

 large as 70, 74, 75, and even 81 and 83 per cent. 



In these experiments so called ''good," "poor," and "bad" eggs 

 were used. These terms will later be defined in definite chemico- 

 physical entities. 



Table 7. — Variation in cleavage of eggs and sperm of different Arbacia individuals. 



Experiment No. 



Age of germ- 

 cells. 



Female. 



Male. 



No. 



of 



male. 



Egg 

 No 

 1. 



Egg 

 No. 

 2. 



Egg 

 No. 

 3. 



Egg 

 No. 

 4. 



Egg 

 No. 

 5. 



Egg 

 No. 

 6. 



Egg 

 No. 



7. 



Egg 



No. 



Maximum 

 difference 

 (per cent). 



8/12 



8/13 



8/14 



8/16 



7/28(1 hour). 

 7/28 (2 hours) 

 8/2 



4i 

 4^ 

 23 

 U 

 5 



u 





 

 



4| 

 4^ 

 23 



5 



u 





 

 



81 

 72 

 75 

 80 

 93 



100 

 83 

 92 



100 



58 

 69 

 70 

 74 

 90 

 98 

 89 

 98 

 100 



1 



4 



3 



99 



100 



100 



92 



97 



77 

 62 

 

 96 

 85 

 88 

 94 

 97 



91 

 53 

 74 

 100 

 95 

 98 

 91 

 98 



92 

 98 

 97 



100 

 97 

 99 



90 

 68 

 75 

 26 

 15 

 12 

 15 

 7 

 



ARBACIA. 



A few observations were made upon Arbacia, which live in much 

 deeper and colder waters. The results are shown in table 7. 



In experiment 8/2, table 7, eggs of different females fertilized by the 

 one male gave 100 per cent cleavage for each. In experiment 7/28 

 all 8 females gave a high cleavage; the maximum difference was 15 per 

 cent at end of 1 hour and only 7 per cent at end of 2 hours. In the 

 other experiments the range of variabihty was much greater — 12, 15, 

 26, 68, 75, and 90 per cent in different experiments. There were low- 

 cleaving females (see experiments 8/12 and 8/13) ; others were sterile or 

 practically so (see 8/12 and 8/13) ; others high-cleaving females. The 

 eggs appeared alike, yet upon actual test they showed a very marked 

 range of variabihty. On some days all the females seemed to be high- 

 cleaving females, as in 7/28; on other days there was marked variation, 

 as in 8/12, 8/13, etc. 



