ANOTHER WAY OF LOOKING AT THE FACTS 507 



Let us consider the difference between the sexes in its 

 simplest expressions, such as we see, for instance, in Volvox, 

 that beautiful sphere of flagellate cells which well illustrates a 

 body in the making. From the ball of cells reproductive units 

 are sometimes set adrift, which divide to form other colonies 

 without more ado. But in other conditions, when nutrition 

 is checked, a less direct mode of reproduction occurs. Some 

 of the cells in the ball become large, well-fed elements the 

 ova ; others, less anabolic, fade from green to yellow, divide 

 and re-divide into many minute units the spermatozoa. 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 seem to be 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 pervades all the cells of the organism." Prof. 

 Wilson notes the extraordinary fact surely of profound import- 

 ance 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 very interesting also to consider cases where the sex 

 changes in the course of life ! Thus in the hag-fish (Myxine 

 glutinosa), according to Cunningham and Nansen, spermatozoa 

 are produced up to a certain size, after which the reproductive 

 organ is wholly ovarian. A case recently described by Prof. 



