12 E. E. JUST. 



sea-water that warming fails after washing although fertilization 

 is still possible. If fertilization be impossible (as in stale eggs) 

 warming also produces no effect. 



Washed or stale eggs warmed in sea-water charged by eggs that 

 have remained in it for some time do not fare any better than 

 those subjected to warmed sea-water; as in the first and second 

 series of experiments this "egg water" makes no difference in the 

 results. 



I think that these facts are incontrovertible. Washing or 

 even residence in sea-water for a short time interferes seriously 

 with the effect of heat in initiating development. 



Study of insemination of dry and washed eggs was made. 

 Apparently there is a difference here of response to the spermato- 

 zoon. The dry egg is more irritable, jelly formation being ex- 

 tremely rapid. This is true of dry eggs inseminated in small 

 quantities of sea-water. This behavior recalls that of Platy- 

 nereis. 



These results, moreover, might suggest that our methods are 

 much too crude in the study of these extremely sensitive cells— 

 the egg and the spermatozoon. 



Summing up we may say concerning the effects of warming on 

 the eggs of Nereis : (i) That while eggs cut out of worms in the warm 

 sea-water form jelly and divide in large numbers, a small per cent, 

 swimming, some remain in the germinal vesicle stage. (2) That 

 at least ninety-eight per cent, of the dry eggs form jelly almost all 

 of which cleave: twenty per cent, become trochophores closely re- 

 sembling the normal. (3) That eggs in "serum" fail to develop 

 except in very small numbers. (4) That washed eggs even after but 

 two or three washings develop if at all in small numbers. 



B. Effect of KCl in the Initiation of Development. 



According to Fischer the eggs of Nereis after treatment with 

 KCl will go through cleavage and produce trochophores. Lillie 

 ('11), however, could not get the eggs after KCl treatment to go 

 beyond maturation. During three seasons this had been my 

 experience. This summer I studied the effect of KCl on washed 

 and unwashed eggs. 



If the eggs be washed two or three times before exposing to 



