674 LECTURE XXIII. 



quite as much nucleo-idioplasm as does the oosphere, and 

 this is without doubt by far the more important matter. 



If, then, the male cell contributes as much nucleo-idio- 

 plasm to the germ as does the female, we should expect 

 to find, that, in cases of cross-fertilisation for instance, the 

 characteristics of the male parent are transmitted as well as 

 those of the female ; and, as a matter of fact, we do. Brooks, 

 however, argues that the facts of hybridisation do not prove 

 the transmission of characters by means of the male repro- 

 ductive cell, and he supports his contention by reference to 

 the fact that the reproductive cells produced in female organs 

 are frequently parthenogenetic, whereas no case of male par- 

 thenogenesis is known. If, he says, a perfect organism could 

 be developed from a male cell, we should have the means of 

 proving that each sexual cell transmits to the offspring the 

 entire organisation of the individual producing it. 



Cases of the male parthenogenesis for which Brooks en- 

 quires, as he believes, in vain, are to be found among plants. 

 We have already stated the grounds for the belief that in 

 plants with externally similar gametes, those gametes are really 

 of two sexes. When, as sometimes happens, in Ulothrix for 

 instance, these gametes, having failed to conjugate, germinate 

 independently, it must be assumed that both male and female 

 parthenogenesis takes place. If such cases be considered 

 inconclusive, no such objection can be taken to the case of 

 Ectocarpus, in which it is possible to distinguish the male 

 planogametes and to ascertain that they are capable of inde- 

 pendent germination, though it must be added that the indi- 

 viduals developed from them are less vigorous than those 

 developed in the ordinary way. It is true that male par- 

 thenogenesis is not known among plants of higher organisa- 

 tion than Ectocarpus, but the explanation is quite simple. In 

 these higher plants the adaptive differentiation of the male 

 cell, especially the reduction of the cytoplasm, is clearly 

 such as to render independent germination quite impossible; 

 whereas, in the case of the female cell, the differentiation 

 which it has undergone is favourable to independent germi- 

 nation. 



