DEGENERATE SEXUAL REPRODUCTION. l8l 



which are impregnated. The discovery referred to is histori- 

 cally Weismann's, while a corroboration is due to Blochmann. 

 It is more important, however, to notice how Minot cleverly 

 adapts himself, and rightly too, to increased knowledge of the 

 facts. The parthenogenetic ovum only retains one polar globule, 

 — one male element is enough; two would be "polyspermy," 

 which is abhorred. 



There was no fear that Rolph would indulge in teleology, 

 rigid necessitarian as he was. Parthenogenesis of ova was to 

 him the more natural process, the sperm a subsequent impor- 

 tation. " There is for the ovum a certain minimal mass, which 

 must be surpassed if it is to develop at all ; and a second minimum, 

 which the ovum must attain, if a female is to be produced." 

 Abundant nutrition of the ovum tends to parthenogenesis, pro- 

 ducing male offspring, as the lower stage ; but if the second 

 limit be attained, resulting in females. In the opposite direc- 

 tion, if the ovum have fewer resources, it requires to be fertilised. 

 Females or males will again result according to the state of the 

 elements. If no fertilisation occur, the dependent ovum must 

 of course die. Rolph is always suggestive, but he erred in 

 regarding the sex-elements too quantitatively, in missing the 

 qualitative antithesis of sex, and the opposition observed in 

 cell-division. 



{d) Strasburger also lays emphasis, in a subtler and more 

 technical way, on nutritive conditions. " In the rare cases of 

 parthenogenesis, specially favourable nutritive conditions may 

 counteract the lack of nuclear plasma." He notes three dif- 

 ferent ways in which this may happen, and also inclines to 

 believe that retention of polar globules would favour partheno- 

 genetic development. It is important to notice how two 

 naturalists, so very different in their manner of attacking a 

 subject as Rolph and Strasburger are, come to this conclusion 

 at least in common, that favourable nutritive conditions favour 

 parthenogenesis. AH the cells in the body tend to multiply, 

 the ova retaining this power develop embryos. 



{e) Weismann has a peculiar right to be heard on the nature of partheno- 

 genesis. For not only has he been for many years an investigator of the tiny 

 daphnids or water-fleas, but he has recently made the important discovery, 

 already noticed, that parthenogenetic ova extrude only one polar globule. 

 There has not been time yet to prove that this is an absolute fact, but the 

 probabilities are strong that it is. Before stating his theory, it is necessary 

 to remember that the "germ-plasma" of Weismann is a specific and essen- 

 tial portion of the nucleus of ovum or sperm, part of which keeps up the 



