264 ARTIFICIAL PARTHENOGENESIS AND FERTILIZATION 
acid (the kind of acid seems immaterial)! 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 HNO,+88 c.c. sea-water. Length of exposure 5 minutes 
15 e.c. N/10 HCI1+85 e.e. sea-water. Length of exposure 5 minutes 
10 c.c. N/10 H.8SO,+90 c.c. sea-water. Length of exposure 8 minutes 
12 ¢.c. N/10 Oxalic acid+88 c¢.c. sea-water. Length of exposure 8 
minutes 
15 e.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 transferenée 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 
ego's 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. 
