332 Geoffrey Smith 



In the Tanaidae, Lamellicornia and Pectiniconiia evidence was 

 prodiiced to show tliat the differentiatiou into hig-h and low males 

 withiu the limits of a species has widely inHuenced the progres- 

 sive diflerentiation among tlie different closely allied species of 

 mauy groups. 



New this means that tlie raodifications in the primary and secon- 

 dary coudition of various speeies which leads to high and low 

 dimorphism within the limits of a speeies, have operated progres- 

 sively in thc evolution of these forms. There can be little doubt 

 that these moditieatious are primarily induced by the conditions of 

 life, cspeeially of nutrition, acting lipon the sexual Organization of 

 the naale. For we know that the sexual Organization is largely in- 

 fluenced by particular conditions of life, by nutrition and most 

 strikingly by the presence of particular parasites, as is evinced in 

 the phenomeuon of Parasi tic Castration. And it is well known to 

 breeders of insects that the size to which the adiilt attains can be 

 very greatly influenced by the amount and qiiality of nutrition 

 supplicd to the larva. 



Now if we assume, as I believe we must, that the })henomenon 

 of high and low dimorphism is an eff'ect largely produced by the 

 influence of exterual conditions on the sexual Organization, it appears 

 that this influence has operated coutiuuously in specilic diifereutia- 

 tion, in other words that these iufluences have become inherited in 

 some manner. But before dismissing this hypothesis as assuming 

 the inheritauce of acquired characters, we must reflect witli wbat 

 we are dealiug. We are dealing with characters that do not pri- 

 marily belong to the body, but to the reproductive Organization. It 

 is the reproductive Organization that is ati'ected in the phenomeuon 

 of high and low dimorphism, and so there is here not the same a 

 priori difriculty in the transmission of such affections, as exists in 

 cases where the body only is influenced. We are ho^vever in need of 

 some material theory by which the moditìcations induced in tlie 

 reproductive system can be transmitted through the gerin cells to 

 succeding generations. A material theory of this nature is, I believe, 

 atforded by a series of facts and cxperimental results, which I 

 hope to describe in a future work, but to which I cannot further 

 advert here. 



