IBLA AND SCALPELLUM. 289 



degree, the parasites of the first three species with the last 

 two species of Scalpellum, in accordance with the affinities 

 of the hermaphrodites. 



When first examining the parasites of 8. rostratum, 

 8. Peronii, and 8. villosum, before the weight of the 

 cumulative evidence had struck me, and noting their 

 apparent state of immaturity, it occurred to me that pos- 

 sibly they were the young of their respective species, in 

 their normal state of development, attached to old indivi- 

 duals, as may often be seen in Lepas ; this, however, 

 would be a surprising fact, considering that 8. rostratum 

 and 8. Peronii are ordinarily attached, in a certain definite 

 position, to horny corallines, and considering that the 

 exact points of attachment in these three parasites, (of 

 which I have seen no other instance amongst common 

 Cirripedes,) namely, between the scuta, would inevitably 

 cause their early destruction, either directly or indirectly, 

 by their living supports being destroyed. Nevertheless, 

 I carefully examined a young specimen of 8. rostratum 

 only thrice as large as the parasite ; and not having very 

 young specimens of 8. Peronii and villosum, I procured 

 the young of closely-allied forms, namely, of 8. vulgare, 

 (with a capitulum only T ^th of an inch in length,) and of 

 Pollicipes polymeries, (with a capitulum of less size than 

 that of one of the parasites,) and there was not the least 

 sign of anything abnormal in the development of the 

 valves. In 8. vulgar e, at a period when the calcified scuta 

 could have been only ^th of an inch in length, (and 

 therefore considerably less than the scuta in the parasites,) 

 the upper latera must have been as much as ^ths of 

 an inch in length, and the valves of the lower whorl cer- 

 tainly distinguishable. 



To sum up the evidence on the sex of the parasites, I 

 was not able to discover a vestige of ova or ovaria in the 

 two male Iblas ; and I can venture to affirm positively, 

 that the parasites of 8. Peronii and 8. villosum are not 

 female. On the other hand, in the two male Iblas, I was 

 enabled to demonstrate all the male organs, and I most 



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