io8 Amos W. Peters. 



this respect also they resemble the adults, except that exhaustion 

 is much more quickly produced. 



Experiments were made to test for phosphorescence before the 

 formation of the paddle plates. A single gastrula was isolated 

 at night in a watch glass. It was still contained in the egg- 

 capsule and showed ciliary movement but no paddle plates were 

 as yet developed. It was placed in the dark-room and, to make 

 the conditions as favorable for the reaction as possible, it was 

 allowed to remain undisturbed for half an hour, when the watch 

 glass was suddenly jarred and a flash resulted. Another flash 

 could not be obtained until after a period of rest. 



Experiments were next made to test for phosphorescence in the 

 segmentation stages and in the egg. It had been several times 

 observed during these studies that embryos from animals that had 

 been kept in the dark-room during the previous day were further 

 advanced when examined the next morning than the embryos 

 from animals kept in diff^use daylight during the previous day. 

 Both lots originated from the same collection and were parallel 

 in conditions except with regard to light. In this experiment the 

 influence of light upon the time of egg laying was also tested. 



August II, 1903,2 p. m. Collected Mnemiopsis. Distributed 

 them into lots A and B, each consisting of several dishes. A was 

 kept in the dark-room. B remained in difluse daylight, later in 

 artificial light, electricity and gas. 



10 p. m. No eggs. 



1 1. 1 5 p. m. Eggs present in lot A of the dark-room. No eggs 

 in lot B. 



A number of eggs were immediately isolated in a solid watch 

 glass and tested by stirring with a glass rod and by jarring, at 

 intervals, in the dark-room. They were examined before and 

 after the series of tests and were found to consist of one-cell 

 stages. No phosphorescence could be detected in these undivided 



eggs- 

 August 12, 12.20 a. m. Cleavage stages from lot A were iso- 

 lated in a solid watch glass. Examination before and after the 

 tests showed that no ciliated (moving) embryo was as yet formed. 

 Stages from one to thirty-two cells were present. After an undis- 

 turbed period in the dark-room stirring with a glass rod elicited 

 phosphorescent flashes, but probably not from all the embryos. 

 12.45 ^- "^- -^o eggs in lot B. 



