LIFE CYCLE OF SIMOCEPHALUS VETULUS. 6 1 



The percentage of males is about ... 42 



The number of times the first brood was purely female 26 



" male 16 



*> .. .. .. i, 



a mixed brood 



undetermined i 



Inst purely female 28 



male 1 1 



a mixed brood 6 



The total number of mixed brood- 



The number producing no mixed broods. 25 



of times the broods immediately preceding and follow- 

 ing mixed broods are of the same sex 9 



The number of times they are of a different sex 4 



The average number in each pure first brood of females . . 6.6 



" " " " males 7 



" " mixed brood 16 



of offspring per individual 39 



' broods 4.3 



' hours between the broods 45.3 



' female broods per individual. . . . 2.1 



" male 1.3 



' females in each female brood 4.5 



' males male 11.9 



produced per individual 15.5 



" females . - 20.7 



" " days each of the 45 females lived 14 



The total number of offspring was slightly over. ... . 1705 



The 45 females under consideration in this experiment were 

 divided into three groups. The first group, consisting of 24 

 individuals, was kept in water taken from an "asexual" culture 

 and were well fed ; the second group of 20 were also well fed but 

 were kept in water taken from a culture which was producing 

 an abundance of males and sexual females; the third group of 

 5 being reared in the same kind of water as the second but were 

 poorly fed. The results of this part of the experiment are 

 given in the following table in which the data have been reduced 



Group i Group 2 Group 3 



Average length of life in days. . .12.4 n.o 



number of broods . 3-6 3-0 10.6 



" female broods 2.1 i.i 5-2 



" females produced 21.6 12.3 43-4 



" males .n-5 *5-6 29.2 



" male broods 9 T -4 3- 2 



"offspring 37-6 26.6 80.6 



% % % 



Mixed broods 10 Ir 



