REPRODUCTION. 655 



direct action of changed conditions, the gemmules derived 

 from the modified parts will be themselves modified, and 

 when sufficiently multiplied, will supplant the old gemmules 

 and be developed into structures possessing the new cha- 

 racters. 



Although the facts of reproduction can be so readily ex- 

 plained on the theory of Pangenesis, still there are objections 

 to its being literally accepted. In the first place, there is no 

 experimental evidence that the gemmules actually exist; and 

 in the second, it requires a great stretch of imagination to 

 conceive that a spore could possibly contain all the gemmules 

 necessary for the development of an individual ; for amongst 

 these gemmules there must be representatives of every cell 

 of the parent in every stage of its development ; and not 

 only these, but dormant gemmules also, transmitted from 

 countless ancestors. 



The theory of Pangenesis has been restated by Brooks in 

 a form so modified as to meet the objection raised to the 

 Darwinian statement of it on the score of the countless 

 number of the gemmules which must be assumed to be 

 present in a reproductive cell. According to Brooks each 

 cell of the body has the power of throwing off gemmules ; 

 but it only exerts this power when, through a change in 

 its environment, its function is disturbed and the conditions 

 of life become unfavourable. The gemmules may be carried 

 to all parts of the body. They may penetrate to the female 

 cell, or to a bud, and the male cell has acquired, as its 

 distinctive function, a peculiar power to gather and store up 

 the gemmules. In the process of fertilisation, each gemmule 

 from the male cell conjugates with or impregnates that 

 particle of the female cell which corresponds to the one which 

 produced the gemmule; or else it unites with a closely re- 

 lated particle, destined to give rise to a closely related cell. 

 When this cell becomes developed in the body of the off- 

 spring it will be a hybrid, and will therefore tend to vary. 

 A cell which has thus varied will continue to throw off 

 gemmules, and thus to transmit variability to the corre- 

 sponding part in the bodies of successive generations of 



