GERMINAL LOCALIZATION IN THE EGG OF CEREBRATULUS. 



it not beiug changed. Larvœ were reared in diffused light. 

 When the room temperature was unusually high, the salt-cellars 

 containing larvae were partly immersed in cold well-water. 



Here in passing it may be mentioned that one very seldom 

 meets with giant eggs (Fig. 1. C) or unsually small eggs (Fig. 

 1. A). In either case they develop normally giving rise to pilidia of 

 proportional sizes. 

 But for the experi- 

 ments, in order to 

 maintain uniformi- 

 ty, eggs of the 

 normal size only 

 were made use of. 



Fig. 1. 

 Eggs with the first polocyte. A, unusually small 



egg ; B, egg of the normal size ; C, giant egg. 



At the outset 

 of the present work 

 it was necessary to 

 determine whether or no the eggs were weakened by being kept 

 long in the water. So long as this point remains unsettled one 

 can never tell whether the cause of defects in the resulting larvse 

 lies in the operation or in decreased vitality {cf. Series T, p. 23). 

 To test the vitality of the egg I took fecundability as a criterion 

 and made experiments in the following fashion. Three lots, each 

 consisting of a hundred eggs, were put in salt-cellars and were 

 seminated one, three, and five hours after release respectively. 

 Then the number of resulting blastulae and the physiological 

 condition of the pilidia were compared. This experiment was 

 repeated seven times and the conclusion was reached that there 

 is no diminution in the fecundability of the egg during the first 

 five hours. Neither was there the slight(.st difference in the 



