264 ARTIFICIAL PARTHENOGENESIS AND FERTILIZATION 



acid (the kind of acid seems immaterial) 1 and then transferred 

 to sea-water, they form membranes, extrude the polar bodies, 

 and often develop into normal larvae after a perfectly normal 

 segmentation. His best results were obtained with the follow- 

 ing mixtures of acids : 



17 c.c. N/10 HN0 3 +83 c.c. sea-water. Length of exposure 5 minutes 

 15 c.c. N/10 HC1+85 c.c. sea-water. Length of exposure 5 minutes 

 10 c.c. N/10 H 2 S0 4 +90 c.c. sea-water. Length of exposure 8 minutes 

 12 c.c. N/10 Oxalic acid+88 c.c. sea-water. Length of exposure 8 



minutes 

 15 c.c. N/10 Acetic acid+85 c.c. sea-water. Length of exposure 5 



minutes 



Under the influence of acid the eggs of Thalassema form a 

 typical fertilization membrane after transference to ordinary 

 sea-water, just like sea-urchin eggs; but whereas the latter must 

 be transferred for a short time to hypertonic sea-water after 

 membrane formation, in order to insure their development, 

 this is not necessary with the eggs of Thalassema. In this 

 respect then the eggs of Thalassema behave like those of 

 Asterina. All the eggs of Thalassema form fertilization mem- 

 branes under acid treatment, but not all of them develop. 

 In the most propitious circumstances 60 per cent of the eggs 

 develop. 



The velocity of maturation and of the onset of cleavage 

 was appreciably less than in the case of the fertilization with 

 sperm. Whereas in the fertilization with sperm the first of the 

 polar bodies was extruded twenty minutes after entry of the 

 spermatozoon, the same event did not take place, when the 

 eggs were exposed to acid, until 45 to 90 minutes after the eggs 

 had been transferred from the acid to normal sea-water. The 

 first cell division took place in 50 to 60 minutes after the entry 

 of the sperm, while it did not occur until two to three and a half 

 hours after the acid treatment of the unfertilized eggs. 



1 He remarks expressly that carbonic acid has just as much effect as any other 

 acid, neither more nor less. 



