DEGENERATE SEXUAL REPRODUCTION. I 85 



In conditions favouring katabolism the males wore themselves 

 out, the females became katabolic enough to do without them. 

 We find the males, where they persist, much smaller than the 

 female rotifers, often extremely degenerate, in one section 

 wholly unknown. Again, from the fact that the interruption of 

 a parthenogenetic series of females by the appearance of males 

 usually occurs in hard times, we may infer that prosperous vital 

 conditions induced parthenogenesis. Why then are not internal 

 parasites parthenogenetic ? They are very generally herma- 

 phrodites, and have moreover gone beyond parthenogenesis 

 to prolific asexual multiplication. 



It is misleading to interpret the occurrence of partheno- 

 genesis as due to "motives" and "important advantages." 

 These are afterthoughts of our importation. It is not easy 

 indeed to keep from metaphorical language which suggests 

 that polar globule-formation is a " contrivance," and partheno- 

 genesis a " device." Such casual words are of little account; but 

 to say, as Weismann does, " that sexual reproduction has here 

 been given up, not by any chance nor from internal conditions, 

 but from quite definite external grounds of utility (Zweck- 

 massigkeitsgrunden)," is to say the least misleading. A species 

 of crustacean is being decimated by enemies, increased multi- 

 plication would lessen the danger of extinction, parthenogenesis 

 is establised, and for every one before producing eggs there are 

 now two^voi/a tout. Against this short and easy method with 

 nature we emphatically protest, and maintain that the origin of 

 parthenogenesis was not for any subsequent advantage, but 

 purely from necessary internal conditions. 



§ 10. The Case of Bees.— Wq have already spoken of the "voluntary 

 parthenogenesis" of bees. All the eggs are supposed to have the power of 

 parthenogenesis, but all are not allowed so to develop. The fertilised eggs 

 develop into queens and workers, the unfertilised give rise to drones. 

 Weismann emphasises the fact that the ova are all alike. "There is no 

 difference between those which are, and are not to be fertilised. The 

 difference first appears after the maturation of the egg, and the removal of 

 the ovogenetic plasma." The state of the polar bodies is not known, so 

 the question need not be complicated by suppositions about them.* Writing 

 before his discovery in regard to parthenogenesis, he says the sine qua non 

 of development is that the nucleus acquire a certain quantity of germ-plasma ; 

 the fertilised ^'gg gets its quantum in the usual way by aid of the sperm, the 

 unfertilised gets^ it by simple growth ; the difference of sex in the result 

 need not be further taken into account. Again we remark, that this matter 

 of a quantum of " germ-plasma," and the two ways of getting it, is a pure 



* See, however, p. 180, note. 



