DENDKOCOMETES PARADOXUS. 355 



There is no evidence of a positive character to show that 

 this is the case, but the absence of any visible boundary line 

 between the sexual cytoplasm and the surrounding somatic 

 cytoplasm is not a definite proof that the distinction does not 

 occur. Many instances could be quoted, both from animal 

 and vegetable tissues, in which each nucleus of a plasmodium 

 has its own sphere of influence in the surrounding protoplasm, 

 even when no cell boundaries can be distinguished. It is, 

 indeed, contrary to our general knowledge and usual concep- 

 tions of cell structures that any nucleus should be entirely 

 independent of the cytoplasm that immediately surrounds it, 

 just as it is that any nucleus should exist entirely free from 

 any cell protoplasm. 



There is one feature of the sexual cells of the Metazoa 

 which at this point in the argument I should like to call 

 attention to. When ova and spermatozoa are ripe, that is to 

 say, when they are ready to perform the only function they 

 possess, they are entirely free from surrounding cell structures. 

 There is no reason to believe that in any case I can call to 

 mind the individual ovum or spermatozoon is in protoplasmic 

 continuity or even contact with other cells. There are no 

 other cells of the animal body, except the white blood- 

 corpuscles, of which the same statement can be made, and it 

 is a feature of some interest and importance that in the 

 Metazoa these cells are in their mature condition independent 

 entities. Now in the Heterokaryota the sexual cytoplasm 

 must be in contact with, and in all probability is in continuity 

 with, the somatic cytoplasm at the time of maturity, and 

 even after the fertilisation has been effected. In this respect 

 then, there is an essential difference between the Metazoa and 

 the Heterokaryota. In the Metazoa a conjugation of the 

 somatic cells and of the somatic nuclei could have no possible 

 effect upon the sexual cells, either before or after fertilisation. 

 In the Heterokaryota, on the other hand, whatever effect the 

 conjugation of the meganuclei and the somatic cytoplasm 

 may have, it must be felt by the sexual nuclei and the sexual 

 cytoplasm with which they are in contact. This consideration 



