COMPLEMENTAL MALE. 241 



than two j and ont of seven or eight specimens, four had 

 not any male ; so that it would appear there is something 

 in this locality hostile to the development of the parasitic 

 males. I have noticed only one instance (that given in 

 fig. 9) in which the males were imbedded a little way 

 apart ; generally they touch each other, and are cemented 

 together : where there are several males, they occur at dif- 

 ferent levels, as measured from the under or upper surface 

 of the chitine border : in one instance of four males ad- 

 hering to one valve, I distinctly perceived that the lowest 

 one was white, pulpy, and recently attached; the two 

 above, which were placed close together and between the 

 same laminae of chitine, were mature ; and the third still 

 higher up, was dead, empty, transparent, and half de- 

 cayed : in some other instances, I have found the upper- 

 most parasites dead, and, together with the surrounding 

 chitine, partially worn away. 



The larva of the male must have a different instinct 

 from the larva of the hermaphrodite ; for the latter 

 attaches itself head downwards to a coralline, whilst the 

 male larva crawling on the scuta of the hermaphrodite, 

 discovers, I presume by eye-sight, the fold in the shell 

 beneath the translucent border of chitine, and there inva- 

 riably attaches itself. Its object in choosing this par- 

 ticular spot, I believe, simply is that the depth or thick- 

 ness of the chitine is there greater, and sufficient for its 

 imbedment, which would hardly be the case elsewhere. 

 This parasite has, as we have seen, no mouth or stomach, 

 and indeed, considering its fixed position and the non~ 

 prehensile condition of its limbs or cirri, a mouth would 

 have been of no service to it, without it had been ex- 

 traordinarily elongated. The male must live on the 

 nourishment acquired during its locomotive larval con- 

 dition ; and its life no doubt is short, but yet not very 

 short, as I infer from the depth to which mature specimens 

 are buried in the chitine border. The full development 

 of the spermatozoa consumes, I suppose, some con- 

 siderable lapse of time. The thorax and limbs, though 



16 



