LIFE CYCLE OF SLMOCEPHALUS VETULUS. 57 



IV. ISOLATION EXPERIMENTS. 



In order to ascertain the course of events in the normal general 

 lite cycle I isolated numerous specimens, at random at first, and 

 kept a complete record of all of their offspring. Some of these 

 will he presented in detail. For convenience all experiments 

 will be referred to by number. 



Experiment i. On June 23 a very large female with the brood 

 pouch full of embryos was isolated. On June 24 a brood of 47 

 asexual females was extruded. These embryos were saved and 

 a first brood secured from each of 25 of them. The remainder 

 died early. There were 13 pure broods of males, the numbers 

 in the broods being as follows 14, 3, 1,3, i, i, i, 2, 2, 2,6, 2, and 7. 

 There were 6 mixed broods as follows: 3 males and 6 females, 

 8 males and 4 females, 6 males and 6 females, i male and 6 

 females, 5 males and 3 females, and 2 males and 4 females. The 

 numbers of females in the pure broods of females were: 4, 5, 6, 3, 

 4 and 2. Now with this single instance before us we might well 

 ask why this great variety in the offspring of the members of a 

 pure brood of 47 asexual females? But in the light of further 

 experimentation along this same line we may reasonably suppose 

 that had the mother of these 47 female embryos lived to produce 

 other broods, some would have consisted of males or at least 

 would have contained males. 



Another female isolated at the same time lived until July 13, 

 when she died with embryos in her brood pouch. Her series 

 of broods is as follows: i male and 6 undetermined, 7 females, 

 15 males, 50 females and i male, 15 males, 9 females, and 13 

 females. The 50 females of the mixed brood were saved and 

 the first brood of each of 19 of them was secured. There were 

 12 broods of males containing 8, 12, 3, 8, 12, 3, 12, 4, 5, 41, 12 and 

 6. There was one mixed brood of 12 males and females, and 6 

 pure broods of females contained 6, 10, i, 3, 2 and 6. 



There seemed to be no constancy as to the ratio of males to 

 females in the offspring of these isolated females, nor in the 

 sequence of broods, some producing males first, some females, 

 and others mixed broods, in a most capricious manner. Hence 

 these miscellaneous experiments demonstrated the desirability 

 of much more extended experimentation to discover if possible 

 what order might underlie this apparent confusion. 



