REPRODUCTION. 661 



karyoplasm from both, and therefore contains both male and 

 female morphological elements. If this be so, every cell of the 

 adult Body contains a material representative of both father 

 and mother, and may be regarded as hermaphrodite. Upon 

 this supposition explanations of the unequal cell-divisions of 

 the ovum giving rise to the polar globules have been based. 

 The ovum before maturation and the spermatoblast before final 

 formation of the spermatozoon being bisexual, each must, it 

 has been suggested, get rid of material derived from one 

 parent before it can fuse with a residuum of the other to make 

 a new cell. The spermatoblast therefore in its first cell- 

 division separates female nuclear matter, and the spermatozoon 

 is a purely male cell ; the ovum on the other hand gets rid of 

 male material in the polar globules, and the mature ovum is a 

 solely female cell ; the union of the two makes a complete her- 

 maphrodite cell from which the new animal develops. This 

 view was supported by the belief that certain insect eggs which 

 develop parthenogenetically did not separate polar globules 

 before commencing to form the embryo. It is now known, 

 however, that such eggs do separate one polar globule, so the 

 theory requires modification. We cannot here go into the dis- 

 cussion of this matter, which is one of the most interesting 

 biological questions. The argument gathers mainly round 

 the theory (Weismann) that each complete cell apart from 

 male and female elements contains two kinds of living mate- 

 rial : one (nuclear plasma) with controlling, reproducing, and 

 hereditary functions; the other (nutritive plasma) with as- 

 similative duties and other powers in various cells, as con- 

 tractility, irritability, and so forth, but exercising these under 

 the influence and direction of the nuclear plasma. In the 

 nuclear plasma itself are two distinct substances a germinal 

 plasma with hereditary functions, and alone found in the just 

 fertilized ovum, and a histogenetic or tissue-building plasma, 

 which is formed by and from the germinal plasma and controls 

 cell-growth, division, and differentiation. The ovum in the 

 first polar globule gets rid of some of its histogenetic plasma, 

 and then in the second polar globule of the male portion of 

 its germinal plasma, and these are replaced by the material 

 brought by the spermatozoon, which is a cell that has in a 

 similar way got rid of some of its histogenetic and germinal 

 plasma. On this theory, moreover, the proportion of the 

 ovum extruded in the polar globules and the ratio of that 



