COMPLEMENTAL MALE. 213 



male of Ibla quadrivahis. But feeling strongly how im- 

 probable it is, that an additional or complemental male 

 should be associated with an hermaphrodite, I will make 

 a few remarks on the only possible hypothesis, if my view be 

 rejected, — namely, that the two parasites considered by me 

 to be exclusively males, are not so, but are independent her- 

 maphrodite Cirripedes, the female organs and ova (which, 

 if present, would have been nearly mature, judging from 

 the presence of spermatozoa in both species) having been 

 overlooked by me in every specimen : and again, that in 

 the animal described as the female I Cumingii, I have, 

 though minutely dissecting several specimens, and find- 

 ing far smaller parts, such as the organs of sense and 

 nervous system, entirely overlooked all the conspicuous 

 male organs, though when I came to /. quadrivahis, and 

 naturally expected to find it likewise exclusively female, a 

 single glance showed me the great probosciformed penis, 

 and by the simplest dissection the vesiculae seminales and 

 testes were exhibited. Such an oversight is scarcely cre- 

 dible; but even if assumed, we have to believe in the 

 extraordinary circumstance of the two parasites being 

 species of an independent genus, not only the very next 

 in alliance to the animals to which they are attached, but 

 in certain most important points, namely, the organs 

 of the mouth, actually deserving a place in the very 

 same genus. Moreover, the two parasites differ from 

 each other, not only in about the same slight degree, but 

 in a corresponding manner, as do the two Iblas to which 

 they are attached ; thus the mouths of Ibla quadrivahis 

 and I. Cumingii are closely similar, (the difference being 

 barely of specific value,) so are the mouths of the two 

 parasites ; but the parts are larger in the hermaphrodite 

 I, quadrivahis, than in I. Cumingii, so are they in the 

 parasites. Again, the most conspicuous character in 

 I. quadrivahis, is the number of segments in the caudal 

 appendages, far exceeding those in the other species of 

 Ibla, as well as of every other pedunculated Cirripede, 

 and the parasite of this species has articulated spinosc 



