HERMAPHRODITISM. 73 



more or less distinct male and female portions, is in a state 

 of less intimate anatomical hermaphroditism than the oyster, 

 where the same caeca of the same organ fulfil both functions at 

 different times. 



This last caution must be kept in view throughout. If the 

 hermaphroditism be very intimate, — that is, if the seats of the 

 ovum- and sperm-production be very close to one another, — it is 

 not to be expected that the development of the two kinds of 

 cells will go on simultaneously. Such would, indeed, be a phy- 

 siological impossibility. Antagonistic protoplasmic rhythms 

 may rapidly alternate, but cannot co-exist. Whether the herma- 

 phroditism be anatomically intimate or no, there is throughout, 

 in varying degrees, a tendency to periodicity in the production 

 of male and female elements. Such a want of " time-keeping " 

 between the sexes is called, in botanical language, dichogamy, 

 and is one of the conditions which render self^fertilisation rarely 

 possible. Both in plants and in animals, the male function has 

 in the majority of cases the precedence. Thus " protandrous 

 dichogamy " (stamens taking the lead) is very much commoner 

 than "protogynous dichogamy," where the carpels are first of 

 all matured. This agrees with the curious cases oi Aiigiosiomum 

 and Cymothoidce already mentioned, where the organ was first 

 male and then female, and indeed with at least most cases among 

 closely hermaphrodite animals. Where the male organs are situ- 

 ated in one part of the body, and the females in another, there is 

 less reason against the production of sperms going on at the same 

 time as the production of ova. The very physiological condi- 

 tions which first determined the position of the ovaries here and 

 the testes there, may remain to render it possible for the two 

 opposing functions to go on at the same time. 



The common snail {Helix) is not only easily dissected, but 

 in the complexity of its arrangements is full of interest. Here, 

 not only are ova and sperms produced within the compass of 

 one small organ, but each little corner of the organ shows 

 female cells forming on the walls and male cells in the centre. 

 It has been justly suggested by Platner that the outer cells 

 are the better nourished; they therefore naturally become 

 developed into anabolic ova. 



§ 7. Self-Fertilisation. — We have noted above, that though 

 male and female organs be present in the same organism, they 

 tend to become mature at different times, and that the more 

 the closer the seats of formation of the two kinds of elements. 



