66 THE AMERICAK MONTHLY ' [Marct, 



yet been furnished, that the posterity will be unvarying. Thus asexual 

 reproduction, or unisexual reproduction, tends to the consei'vation of 

 ancestral form, and does not lead towai'd diversity from the ancestral 

 type. Sexual reproduction, on the other hand, is plainly the cause of 

 variation, as seen in the history of plant propagation from seedlings, 

 and also from the breeding of domesticated animals. Thus no one feels 

 any confidence in assigning the breed of mongrel dogs, though he w^ould 

 have no hesitation in recognizing that of one true bred. The disturb- 

 ing influence of an ill-bred male is believed by breeders to affect not 

 merely the immediate offspring, but even subsequent births, so that 

 very great caution is exercised in crossing when an effort is made to 

 introduce a new variety. It is thus very likely that the meaning of sex- 

 uality will be connected with the cause of diversity and resemblance in 

 the animal kingdom. 



The recent literature upon this subject has assigned to the female sex 

 the function of retaining and transmitting the racial peculiarities which 

 appear in the offspring, and has assigned to the male sex the office of 

 causing the change, slight though it be, by which the offspring departs 

 from the racial type, and which divergence seized on by natural selec- 

 tion may become the starting-point of a new species. The full history 

 of the egg is not known in all cases, but it is likely that some of the 

 material of the egg is set a.side at a very early date in the segmentation, 

 and this unused portion is carried along in the developing body to be- 

 come its generative tissue. If such were the case parthenogenesis as 

 the propagation of an unvarying posterity becomes intelligible, for the 

 offspring must be like the parent since it is produced from some of the 

 same substance. The origin of ova may thus be compared with repro- 

 duction among the protozoa : in amoeba a spherical nucleated cell di- 

 vides into two, which separate and go each upon its separate history ; in 

 the metazoa the &^^ cell subdivides into two, one portion goes on and 

 divides and produces a member in the genetic series, the other remains 

 dormant, and the date of its activity is the date of arrival of the parent 

 at maturity. Each generation thus at its birth prepares for the succeed- 

 ing generation, and the chain is one of children like their parents. 

 Brooks, Weismann, and others claim that this succession would permit 

 of no variation. Geddes is not certain that this is true so absolutely, but 

 still such a mode of descent would allow but little variation. Sexual re- 

 production also finds its representative in the reproduction of the proto- 

 zoa, for conjugation has very long been considered and taught to be in 

 some sense an equivalent process, and this is not the only form of the 

 union of two individuals for the purpose of reproduction, for in the 

 myxomycetes numerous amoeboid bodies unite to form one body, and 

 in the algse and low animals there is the union of two unlike members 

 in conjugation. 



Passivity then is the function of the female and activity of the male, 

 and this is the keynote of our authors' work. In the elaboration of this 

 thesis they make very many observations which are of the most fasci- 

 nating interest, but cannot receive attention here. According to the 

 view of this very recent English writing on the subject, we may regard 

 the ovum as a potential organism in which the tendency to repose is 

 very strong and whieh contains a large store of nutritive material, while 

 the spermatozoon is an organism in which the tendency to activity is 



