SPECIAL PHYSIOLOGY OF SEX AND REPRODUCTION. 245 



tion are necessarily associated with menstruation in Homo, there can be 

 little doubt of the general physiological parallelism of all three processes. 

 At present there may be said to be two rival theories. According to the 

 first of these, the process is viewed as a kind of surgical " freshening" of 

 the uterus for the reception of the ovum, whereby the latter during the 

 healing process can be attached safely to the uterine wall. The other view 

 is exactly the reverse of this. Its upholders regard the growth of the 

 mucous coat before this commencement of the flow as a preparation for the 

 reception of an ovum if duly fertilised, and the menstrual process itself as 

 the expression of the failure of these preparations, — in short, as a consequence 

 of the non-occurrence of pregnancy. A decided majority of gynaecologists 

 appear to incline to the latter view. 



The process may, however, be expressed in more general, and at the 

 same time more fundamental terms. If the female sex be indeed pre- 

 ponderatingly anabolic, we should expect this to show itself in distinctive 

 functions. Menstruation is one of these, and is interpretable as a means of 

 getting rid of the anabolic surplus, in absence of its consumption by the 

 development of offspring, — ^just as it is intelligible that the process should 

 stop after fertilisation, when replaced by the demands of the practically 

 parasitic foetus. In the same way, the occurrence of lactation, after this 

 internal parasitism has been terminated by birth, is seen to be reasonable. 

 The young mammal is thus enabled to become what is practically a 

 temporary ecto-parasite upon the unfailing maternal anabolic surplus ; and 

 when lactation finally ceases, we have the return of menstruation, from 

 which the whole cycle may start anew. So in the widely different yet 

 deeply similar world of flowers, the distinctly anabolic overflow of nectar 

 ceases at fertilisation, and the surplus of continual preponderant anabolism 

 is drafted into the growing seed or fruit. 



§ 3. Sexual Ujiion. — In a previous chapter we have noted 

 the passive and random way in which the sex-elements of many 

 of the lower animals are liberated, and the chance manner in 

 which they are brought together by water-currents and the like, 

 though this may not be quite so common as our ignorance 

 leads us to suppose, witness the recent observation of the 

 sexual intertwining of Asterina and of Aiitedon. Yet more 

 in plants is the liberation of male elements, and notably 

 that of pollen -grains, a passive dehiscence, and fertilisation 

 a matter of chance, only reduced by the prodigal wealth 

 of material. Secure as the methods of fertilisation of flowers 

 by the aid of insects often are, the margin of risk is wide ; 

 and this is yet more marked when the pollen is carried 

 by the wind. It is true that, both in plants and animals, there 

 are subtle attractions between the essential elements, but this 

 is only at a close range ; and the external union is in many 

 cases none the less random. 



It must be allowed that the primary importance of the 

 timely encounter of the ovum and spermatozoon has per- 



