THE CELL AND ITS CONSTITUENT STRUCTURES. 157 



Fuc2is is probably a long way removed from the main series 

 of plants, an opinion already shared by many people on 

 other grounds. Indeed, it seems tolerably clear that there 

 is nothing of the nature of that alternation of generations 

 in Fticus which is so eminendy characteristic of the main 

 plant-series. 



A phenomenon of such general occurrence as this of 

 reduction is obviously one of profound importance, and it is 

 scarcely to be wondered at that the divisions which are 

 concerned in effecting it should have formed the subject of 

 very many investigations. It was, and is still, hoped that 

 some definite evidence might be forthcoming as to the way 

 in which hereditary characters are transmitted and new 

 qualities arise. For it has been tacitly assumed by nearly 

 every one who has written on this subject that the teleo- 

 logical explanation of the whole process is in some way 

 bound up with that of heredity. The only positive and bare 

 inference however is that since the male pronucleus con- 

 tributes the same number of chromosomes as the female a 

 numerical reduction is necessary at some period in each 

 sexual cycle, unless the number of chromosomes is to in- 

 crease in geometrical progression in every succeeding sexual 

 generation. 



But with the general admission that a reduction is 

 effected, all agreement between various investigators ceases. 

 There is hardly less difference in opinion as to the manner 

 in which the process is actually brought about than as to 

 the meaning of the various stages. And once more, when 

 we take a general survey of the facts, I think we see that 

 the same result may be accomplished in a variety of ways ; 

 hence at present it is perhaps premature to lay too much 

 stress on the details of this or that set of observations (how- 

 ever accurate they may be for the particular subject of 

 investigation), in endeavouring to frame general theories. 

 And so, though theorising is very inviting in such a subject 

 as this, I think I shall best serve the purposes of this dis- 

 cussion by bringing before you some of what I conceive to 

 be the most salient points characteristic of the reduction 

 divisions in plants and animals, only criticising those views 



