MALE. 197 



can seldom be made distinctly out ; but having cut one 

 specimen transversely across the thorax, they were as 

 plain as could be desired, lying parallel and close to each 

 other above the rectum, (the animal being in the position 

 as drawn,) and therefore in their normal situation. Each 

 had a diameter four times as great as that of the rectum. 

 In this individual the contents seemed (whether from 

 decomposition or state of development, or from my not 

 having used high enough power, I know not,) merely 

 pulpy ; but I have since found, in another specimen, 

 masses of the most distinct spermatozoa, with the usual 

 little knots on them, associated with numerous cells, about 

 as large as and resembling those which I have examined in 

 living Cirripedes, and from which I have every reason 

 to believe the spermatozoa are developed. The vesiculae 

 seminales unite and terminate under the two extremely 

 minute caudal appendages, and here I think I saw an orifice; 

 but there is certainly no projecting, probosciformed penis. 

 Having dissected the six specimens with the utmost 

 care, and having scrupulously examined the ovaria in 

 other Cirripedes during their early stages of development, 

 even before the exuviation of the larval locomotive organs, 

 and in specimens of smaller size than the male Ibla, I 

 am prepared to assert that there are no ovaria, and that 

 these little creatures are exclusively males. It should be 

 borne in mind, that in some of the specimens there were 

 perfect spermatozoa in the vesiculae seminales (as likewise 

 in some of the males of I. quadrivalvis), and, therefore, 

 if these individuals had been hermaphrodites, their ova 

 would have been, at this period, well developed, and ready 

 for impregnation : in this state it is almost impossible that 

 they could have been overlooked. Moreover, it is probable 

 that such ova would not have been very small, for the 

 larvae whence the parasitic males are derived, attain (as 

 might have been inferred from the known dimensions of 

 their prehensile antennae, and as we shall show actually is 

 the case in I. qiiadrivalvis,) the size common amongst 

 ordinary Cirripedia. 



