J. W. SCOTT. 



80 



60 



40 



20 



3. Frequent and moderate squirting after thirty to forty-five 

 minutes seems more effective than one hard squirting, after the 

 same time. Compare experiments 3 and 4. 



A comparison with fertilized eggs is of interest. The normal 

 egg throws off the first polar body in less than thirty minutes 

 after fertilization, and the first cleavage appears about thirty 

 minutes later. According to Loeb's l view, the sperm in the 

 case of parthenogenetic eggs acts simply to hasten, or accelerate, 

 processes which are already present in the egg. It hasf requently 

 been noticed that the unfertilized egg of Ampliitritc, if left undis- 

 turbed in sea-water, will often show some phenomena of differ- 

 entiation. Assuming Loeb's theory as a working hypothesis, we 

 should expect artificial means to be slower than fertilization. 

 This proves to be the case ; fertilized eggs develop cilia sooner 



\ 



20 



40 



60 80 



FIG. 2. 



IOO 



I2O 



than those squirted. Sometimes there is not much difference in 

 AmpJiitrite. Presumably, then the two critical periods mentioned 

 correspond to processes in the normal egg that are active about 

 the time for the appearance of the first polar body and the first 

 cleavage ; there is the same relative time between them. Further 

 work is needed to prove this. Delage 2 states that the starfish 

 egg is highly susceptible to " artificial fertilization " between the 

 breaking down of the germinal vesicle and the appearance of the 

 first polar body. 



However this may be, it is certain that there arc processes of 

 differentiation going on in the unfertilized eggs of Amphitrite which 



'Loeb, J., Am. Jour, of P/iys., 1901, Vol. IV., No. IX. 



2 Delage, Y., Archiv d. Zvol. Exper. et. Gen., 1901, T. IX., Nos. 2-3. 



