170 AMPHIMIXIS OR ESSENTIAL MEANING OF [XII. 



the male germ-cells ; with the knowledge we now possess 

 there can be no doubt upon this question. Not every unicellular 

 germ is phyletically an ovum. We ought to recognize and 

 apply to the botanical world the difference between partheno- 

 genesis and asexual reproduction from unicellular germs. This 

 distinction has not been made with any completeness, as we 

 see in the passages quoted above from Professor Vines, and 

 hence it is impossible to draw any safe conclusions from the 

 asexual reproduction of the above-named fungi and from the 

 fact of the phyletic development of numerous genera and 

 species,— as to the amount of variation provided by heredity in 

 parthenogenetic reproduction. The conditions of life among 

 fungi are well known to differ markedly from those of most 

 other plants, and it is not inconceivable that these may be 

 associated with the disappearance or absence of amphigony ; 

 for the peculiar conditions of life may exercise an unusually 

 strong direct influence upon the germ-plasm, and may thus 

 render it variable. We know that variability is induced in 

 other plants when they are submitted to very favourable 

 nutritive conditions. But the researches of botanists must not 

 be anticipated by these conjectures. 



The Origin of Parthenogenetic Eggs front those vuhich require 

 Fertilization. 



As I have already stated, parthenogenesis must have arisen 

 from sexual reproduction. Those cells which develope partheno- 

 genetically are female germ-cells which have gained the power 

 of producing new organisms without fertilization. We must 

 now enquire how this change has been brought about. 



I must first allude to the gonoplastid theory, of which the 

 principle has been proved to be untenable, but which is never- 

 theless correct in certain aspects, at least in the form in which 

 Balfour conceived it. This thoughtful writer expressed the 

 idea that the arrangement of polar bodies might have been 

 brought about by nature, in order to prevent parthenogenesis. He 

 therefore imagined that parthenogenetic development would 

 ensue if the polar bodies, containing the supposed ' male prin- 

 ciple,' remained in the Qgg. If, however, the facts are somewhat 

 different, in so far as the polar divisions of the egg have been 



