WHAT DETERMINES SEX? 115 



pillars the blood has a different colour in the 

 two sexes, being green in the females and 

 bright yellow or colourless in the males ? 

 Dr. Francis Hare has made out a very good 

 case for the theory that menstruation repre- 

 sents a periodic discharge of carbonaceous 

 anabolic surplus in the blood which is ear- 

 marked, so to speak, for the organically 

 anticipated offspring. What but a physio- 

 logical theory is suggested by the state of 

 affairs described by G. du Plessis in Grubea 

 protandrica, one of the Syllid worms, which is 

 male in autumn and winter, female in spring, 

 and neuter in summer ? 



It is interesting to consider those cases 

 where the sex changes in the course of life ! 

 A case recently described by Prof. F. Braem 

 is very suggestive. He experimented with 

 a simple Annelid worm, Ophryotrocha puerilis. 

 Taking a female which had ripe eggs and 

 showed no trace of hermaphroditism, he 

 divided it into two. The head portion, with 

 thirteen segments, was isolated. In three 

 weeks it had regenerated seven segments 

 with parapodia. It was then killed and 

 found to be male. The ova had mostly 

 disappeared from the reproductive organs, 

 leaving only a residue, and a functional 

 testicular portion had developed, which was 

 producing spermatozoa. Braem suggests that 

 in consequence of the amputation the very 

 young, indifferent germ-cells had developed 

 into male cells, which require less subsistence 

 than ova. What is certain is that the re- 

 productive organs had changed from pro- 

 ducing eggs to producing sperms, and such 



