102 BALANID.E. 



rior pairs of cirri, either on one or both sides, were in an 

 almost rudimentary condition, being of small size and 

 having a shrunk and wasted appearance. In six out of 

 these seven specimens, the probosciformed penis was quite 

 short and abruptly truncated, as if from abortion. By 

 cutting off the truncated apex, and cleaning the external 

 tissue, I ascertained that it was imperforate, apparently in 

 all the cases, and I am certain of this fact in several of the 

 cases. In three of the specimens, I examined the vesiculae 

 seminales j in one, I found some spermatozoa, but cohering 

 together in a peculiar manner ; in the second, there were no 

 spermatozoa; and in the third, the vesiculae were shrunk, 

 empty, and quite rudimentary in size. So that these three 

 individuals certainly could not have impregnated their own 

 eggs ; nevertheless, within the shell of these very three, there 

 were perfectly developed larvae : I am led to conclude from 

 this fact, that adjoining specimens in a perfect condition had, 

 by means of their long probosciformed penis, effected the 

 fecundation of their imperfect neighbours. I need only 

 further add, that some out of the above six specimens, with 

 more or less aborted cirri and imperforate male organs, 

 were infested by a peculiar parasite, allied to Bopyrus,* 

 and that these specimens did not contain ova. 



JSletamorphoses and Homologies, throughout the Order of 



Thoracica. 



In my former volume, the metamorphoses were described 

 under three principal stages or heads ; but whether these 

 three included all the main changes, I was then hardly able 

 to conjecture. But now I have reason to believe that such 

 is the case, for in the genus Cryptophialus, belonging to 

 the Abdominalia, the whole course of the metamorphosis, 

 from the egg to the pupa, takes place within the sack of the 

 parent ; and I found, when having, on the coast of South 

 America, numerous specimens to examine, that the egg-like 

 larvae (PI. 24, fig. 15 — 18) could be naturally grouped into 



* I have given a short notice on this parasite, in my former volume on the 

 Lepadidse, in a foot-note to p. 55. 



