1890.] 135 [Ryder> 



The new external conditions constitute a continuously acting series of 

 stimuli provoking the action and reaction of the chromatin, achromatin, 

 and cytoplasm upon each other, as has been rendered probable by the 

 studies of Boveri and Watase. The isolation of the egg makes it inde- 

 pendent ; its cleavage products now cohere and the whole plan of its 

 fragmentation depends upon its using every particle of its cytoplasm as 

 reciprocally nutritive material for the maintenance of the integrity of the 

 whole. 



Maturation is truly the proper name for the process of the extrusion of 

 polar bodies, and it may be that in some cases the polar bodies may be 

 large enough to merit the name of protova, especially the first one, and 

 that a large enough cytoplasmic field may exist around its nucleus to 

 attract spermatozoa. Yet the polar bodies are nevertheless to be regarded 

 as abortive attempts at the production of spermatozoa. 



It may also be that the male condition characterized by the assumption 

 by the elements of that sex of a monad-like flagellate form, is really an 

 attempt at the recapitulation of the most ancient ancestral monad iform 

 condition. In the female we have seen that the attainment of such a 

 condition is abortive, but enough is left in the disguise of the polar bodies 

 to represent a reminiscence of the lowest phase of organic evolution. 



We have now recapitulated all the important and difficult queries that 

 have arisen in regard to the meaning of the polar bodies, which we also 

 now see probably have a phylogenetic significance. 



The evolution of complicated apparatus and processes for the emission 

 of the sexual products, when mature, is only an accessory and a secondary 

 consequence of the continuous series of processes described above, and 

 whicn has also proceeded pan passu with the divergence in the morpho- 

 logical and physiological characters of the products of the two sexes. 

 The primary sexual characters and probably also the secondary ones have 

 been evolved in response to the all-important requirement of most 

 efficiently disposing of the sexual products. The habit of copulation 

 itself must have so arissn, and the stimulus effecting the discharge of the 

 sexual products finally acts through the sensorium and through the recip- 

 rocal contact'of the nerve terminations in special dermal tracts concerned 

 in copulation in the two sexes. 



In this way it must be supposed that eventually the sexual passion 

 became intensified as the provisions for effecting the union of the sexual 

 cells became more elaborate, and as the parent-body became more and 

 more differentiated and specialized to take a more and more important 

 share in this process. The presence of the germ cells has undoubtedly 

 reacted upon the soma or parent body so as to intensify the tendency 

 towards a greater differentiation of the primary sexual organs, and this 

 through the sensorium and its sensory terminals. 



It is interesting to reflect that the tendency to a repression of the male 

 traits in the ovum has been manifested in the adult organization of the 

 two sexes in Melazoa. The assertion of some writers to the effect that 



