536 LIFE : OUTLINES OF GENERAL BIOLOGY 



reproduction occurs. Some of the cells in the ball become large, 

 well-fed elements — the ova; others, less anabolic, fading from green 

 to yellow, divide and redivide into many minute units — sperma- 

 tozoa. The large cells of one colony are fertilised by the small cells 

 from another. Here we see the formation of dimorphic reproductive 

 cells in different parts of the same organism. But we may also find 

 Volvox balls in which only ova are produced, and others in which 

 only sperms are produced. The former are more vegetative and 

 nutritive than the latter; we call them female and male organisms 

 respectively; we are at the foundation of the differences between the 

 two sexes. 



What we are suggesting is a physiological way of looking at the 

 problem, and the idea that the sex-contrast expresses a physiological 

 alternative. This is suggested in various ways. For instance, there 

 is the sometimes striking evidence that sex is "a quality that per- 

 vades all the cells of the organism". Prof. Wilson notes the extra- 

 ordinary fact — surely of profound importance — that: "In the 

 Mosses the Marchals demonstrate that all the products of a single 

 spore are likewise immutably determined, since new plants formed 

 by regeneration from fragments of the protonema, or from any part 

 of the gametophyte, are always of the same sex." 



It is interesting also to consider cases where the sex changes in 

 the course of life ! A case carefully 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 repro- 

 ductive organs had changed from producing eggs to producing 

 sperms, and such cases appear to us to favour the view that the sex- 

 difference is fundamentally physiological. 



CoNXLUsioN. — In conclusion, our view is that the difference 

 between an ovum-producer and a sperm-producer is fundamentally 

 a difference in the balance of chemical changes, i.e. in the ratio of 

 anabolic and katabolic processes, which may, of course, have its 

 structural expression in the relation of nucleoplasm and cytoplasm. 

 Nor do we leave this difference in metabolism-rhythm as a mere 

 vague phrase, for we see its analogue in the contrast between the 

 ovum and the spermatozoon (though it is quite unwarrantable to 

 think of these as being in themselves respectively female and male 



