214 IBLA QUADRIVALV1S. 



appendages, far larger than the barely visible, non-articu- 

 lated pair in I Cumingii. 



Considering the whole case, there seems no room to 

 doubt the justness of the conclusion arrived at, under the 

 former as well as under the present species, namely, that 

 these little parasites are the males of the two species of 

 Ibla to which they are attached ; — wonderful though the 

 fact be, that in one case, the male should pair with an 

 hermaphrodite already provided with efficient male organs. 

 It is to bring this fact prominently forward, that I have 

 called such males, Complemental Males ; as they seem to 

 form the complement to the male organs in the herma- 

 phrodite. We look in vain for any, as yet known, analogous 

 facts in the animal kingdom. In the genus Scalpellum, 

 however, next in alliance to Ibla, in which, consequently, 

 if anywhere, we might expect to find such facts, they 

 occur; and until these are fully considered, I hope the 

 conclusions here arrived at, will not be summarily rejected. 

 Although the existence of Hermaphrodites and Males 

 within the limits of the same species, is a new fact 

 amongst animals, it is far from rare in the Vegetable 

 Kingdom : the male flowers, moreover, are sometimes in 

 a rudimentary condition compared to the hermaphrodite 

 flowers, exactly in the same manner as are the male Iblas. 

 If the final cause of the existence of these Complemental 

 Males be asked, no certain answer can be given ; the 

 vesiculse seminales in the hermaphrodite of Ibla quaclri- 

 valviSy appeared to be of small diameter ; but on the 

 other hand, the ova to be impregnated are fewer than in 

 most Cirripedes. No explanation, as we have seen, can 

 be given of the much simpler case of the mere separa- 

 tion of the sexes in Ibla Cumingii ; nor can any expla- 

 nation, I believe, be given of the much more varied 

 arrangement of the parts of fructification in plants of 

 the Linnean class, Polygamia, 



