THE CONSEBVATION OF LIFE 233 



nucleus, the ' primary constituents ' of a complete organism, 

 it cannot develop one out of itself because of the absence of a 

 sufficiency of food. If, therefore, the spermatozoon is not to 

 perish before it has fulfilled its mission it must join with an 

 ovum. Only in an ovum will it be possible for it to develop its 

 individual faculties. The male germ is, therefore, of necessity 

 dependent upon the fertilization process. 



It is different with the ovum. Though we know that it has 

 been built for fertilization, this process is far from being an 

 absolute necessity, for there are numerous cases known of 

 natural and artificial parthenogenesis in which eggs develop 

 into complete individuals without preceding fertilization. 



When I said before that the male spermatozoon is of necessity 

 dependent upon the fertilization process the statement was only 

 conditionally true, for we know a case in Nature, that of an 

 Alga (Ectocarpus siliculosus), in which not only the female germ- 

 cells are able to develop parthenogenetically, but that also the 

 male sex-cells can, under certain circumstances, reach inde- 

 pendent development. How is this unique behaviour to be 

 explained ? In Ectocarpus siliculosus the difference in size 

 between the germ-cells is not considerable, for the spermatozoa 

 possess a proportionately large amount of protoplasmic substance, 

 and this is no doubt the reason for a certain independent 

 development. Nevertheless, the independent formation of the 

 separated germ-cells is only an act of necessity, and the little 

 male plant always grows into a poorly-developed organism, 

 corresponding to the smaller size of the male-germ. 



The most important lesson to be learnt from this observation 

 is that ovum and spermatozoon are formations fundamentally of 

 equal value, normal cells of which each carries within itself the 

 ' primary constituents ' of a complete organism and is able, 

 under certain circumstances, to develop them independently. 

 Generally, however, we find that the sex-cells are dependent 

 upon conjugation. Nature, indeed, makes all preparations, if 

 I may use such anthropopathic expression to describe its blind 

 work, for forcing fertilization and mixing the qualities. Thus 

 we see that in progressing evolution the independent develop- 

 ment is made more and more difficult and even impossible to 

 both spermatozoon and ovum. This is effected in the male 



