Phosphorescence in Ctenophores. 109 



1.20 a. m. Many embryos in lot A were becoming gastrulae. 

 Also many undeveloped (dead r) one-cell stages were still present 

 in lot A. 



1.30 a. m. No eggs in lot B. 



2.20 a. m. Some eggs in lot B. Some of these were isolated 

 in solid watch glasses, examined before and after testing for 

 phosphorescence and found to be in one-cell stages. 



2.40 a. m. No phosphorescence was detected in the one-cell 

 stage isolated above from lot B. 



An interesting result of this experiment is the difference of 

 about three hours in the time of the laying of the eggs between 

 lots A and B; lot A having been in the dark longer, deposited eggs 

 sooner. In a subsequent experiment it was observed that animals 

 kept in the dark from 9 a. m. had not yet deposited eggs at 10.30 

 p. m., although eggs were present the next morning. Hence the 

 deposition of eggs does not seem to occur after simply a given 

 number of hours of darkness. The indications favor the view 

 that the deposition of eggs takes place in accordance with the 

 daily rhythm of light and darkness, deposition occurring in the 

 dark period, and being capable of retardation by light. 



III. INFLUENCE OF CERTAIN FACTORS ON PHOSPHORESCENCE. 



I. Agitation and Light. 



In determining what factors influence phosphorescence it has 

 been found convenient to deal with agitation and light together. 

 Preliminary tests showed that ctenophores removed to the dark- 

 box at once from their native sea-water, where they had been 

 exposed to direct sunlight, were not immediately phosphorescent. 

 However, they became so after remaining in the dark for some 

 time. Similar observations were first made on Beroe by Allman 

 ('62) and subsequently by Panceri ('72). The above fact was the 

 starting point for a series of experiments in which both light and 

 agitation were factors. 



Experiment I. Lots A and B having been exposed to direct 

 sunlight for about one hour, were both placed in the dark-box at 

 the same time. The ctenophores in A were then continually 

 agitated with a glass rod, while B was left undisturbed except for 

 momentary tests made at intervals. A phosphoresced first in 

 2.5 minutes; B in 3.0 minutes. 



