182 



Scientific Proceedings (60). 



Each line is propagated by selecting from the first brood of a 

 young female on the day this first brood is released from the brood 

 pouch. The selected young are placed each in an individual 

 bottle with standard food and though examined daily are otherwise 

 undisturbed until the first brood of the next generation appears, 

 when the selections are made as before. Several of these lines 

 have passed the 95th generation and one has just reached the one 

 hundredth generation without the appearance of sexual forms in 

 any generation. All the individuals of the first broods of each 

 generation have been under more or less close scrutiny until they 

 themselves reproduced. If any, or at any rate, many males had 

 occurred they must certainly have been noticed. The method of 

 rearing the daphnids (in individual bottles) has precluded the 

 possibility of sexual reproduction even had males been abundant 

 in the cultures. 



There is no evidence of decreased vigor or loss of vitality in the 

 lines. Hence it appears that there is not a necessary sexual cycle 

 in the reproduction of this daphnid. Male daphnids, apparently 

 of this species, have been collected at Cold Spring Harbor since 

 this work was begun. These facts would lend evidence (if addi- 

 tional evidence were necessary) that the sexual cycle in Daphnia 

 pulex is not an inherent necessary thing but that it is determined 

 by environment. 



Simocephalus , presumably Simocephalns vetuhis, has been 

 reared for 76 generations in one line, likewise without the appear- 

 ance of sexual forms. 



113 (930) 



The comparative importance of pressure and of toxicity of trikresol 

 in subdural injections of sera. 



By C. B. Fitzpatrick, J. P. Atkinson, and A. Zingher. 



[From the Department of Health Laboratories, New York City.] 



As a result of several accidents reported as being due to intra- 

 spinal administration of antimeningococcus serum containing 

 trikresol, a number of tests were made on dogs to determine if 

 possible whether the fatal results were due to the influence of 

 trikresol in the serum, to the serum per se, or whether they were 

 due to pressure. 



