SPAWNING HABITS OF CHyETOPLEURA APICULATA. 235 



discovered that they could not be had at all times. They were 

 obtained plentifully from July 12 to 20 and then spawning sud- 

 denly ceased. The writer naturally supposed that the end of the 

 spawning season had been reached and that no more eggs could be 

 expected that summer. However, experiments were continued at 

 intervals of a few days, and at the approach of the next full moon 

 eggs were again obtained. This time the period of spawning ex- 

 tended from August 8 to n, inclusive. No eggs were obtained 

 after the eleventh of August, although numerous attempts to induce 

 further spawning were made. By referring to the table which 

 follows, it will be seen that spawning began at the approach of full 

 moon in July and continued thereafter for approximately one week 

 (or until the third quarter), then ceased for a time to begin again 

 in like manner at the time of the next full moon, thus indicating a 

 distinct lunar periodicity. 



TABLE. 



Phase of moon. Dates on which spawning occurred, summer of 1919. 



Full moon July 12. 



July 13- 

 July 14. 

 July 1 6. 



Third quarter July 20. Spawning active, apparently at maximum, many 



eggs laid by large proportion of females. Spawning be- 

 gan at 8.00 P.M. and continued until 2.00 A.M. 

 August S. Spawning occurred about 9.00 P.M. No eggs 

 had been obtained during the preceding two weeks which 

 included the new moon and first quarter. 



Full moon August 10. 



August ii. 



No eggs obtained after August n, although several 

 trials were made. 



During the summers of 1920 and 1921 experiments were con- 

 tinued for the purpose of determining the limits of the spawning 

 season and the relation of spawning activity to the cycles of the 

 moon. As a result of these experiments the time limits of the 

 spawning periods were found to lie much less restricted than the 

 data collected in 1919 indicated. In general, the data obtained dur- 

 ing the last two years show that eggs may be had in small quantities 

 at almost any time. By far the greatest spawning activity, how- 

 ever, comes at the approach of full moon and continues for ten 



