318 



Geoflfrey Smith 



n large seiics of males, but it appears that a similar phenomeuon 

 of dimorpliism also occurs iu this species. Figures of low, middle 

 and high males are given iu Textfigures 6, 7 and S respectively. 



C. General Bemarks. I do not 

 doubt that the eases of facultative 

 high and low dimorphism deseribed 

 give US the clue to the meaning 

 of the phenomeuon in general. For 

 if we suppose that the males of 

 Inaclius did not go on growing 

 after assuming the mature coudi- 

 tion, but that the whole period of 

 growth was relegated to a larvai 

 state, we should have a case of 

 definitive high and low dimorphism iu the males. As it is, howe- 

 ver, we have the resumption in the middle males of a kind of 

 larvai immature condition which occurs after a temporary assumption 

 of the sexual state in the low degree. This phenomeuon points to 

 an antagonism between growth and sexual maturity as the expla- 

 nation of the occurrence of high and low dimorphism, an antagonism 

 which is widely evidenced in organic nature. But to go further iute 

 this matter at present would be a digression from our main descrip- 

 tive theme. 



Fig. 8. 



3. Defluitive high and low dimorphism. 



A. Gnatl/ia maxiUaris. In a small paper in this journal (6 I 

 deseribed some facts which appeared to show that there were two 

 criticai periods for the transformation of the larva into the aduli 

 male, firstly when the larva had reached about 2 mm. in length and 

 again at about 5 mm. It will be remembered that the larva of 

 Gtwthm which undergoes metamorphosis into the adult is a swollen 

 ectoparasite on fish known as Praniza, but another larvai form occurs 

 which I called the giant segmented larva, and this is most fre- 



