444 CASWELL GRAVE 



enteric cavities and thus frees itself from the burden of con- 

 stantly manipulating the yolk. 



5. A study of the literature of echinoderm embryology in- 

 dicates that some process of yolk segregation probably takes 

 place during the development of all 3'olky eggs, but there is 

 such a lack of conformity in the processes found in different 

 species as to indicate that the process peculiar to each species 

 has been independently acquired — that there is no genetic 

 continuity in processes of yolk segregation found among echino- 

 dernis. 



6. A close correlation between the volume of yolk material 

 of an egg and the period of its larval development seems to exist 

 among echinoderms. 



7. The spawning activities of Ophiura brevispina take place 

 at or near eight o'clock p.m. with the advent of darkness. They 

 are to be correlated in part at least with the nocturnal habits 

 of the species. 



