IBLA QUADR1VALVIS. 203 



same individual. As males in other classes of the animal 

 kingdom often retain some female characters, so here 

 (though the case is not strictly analogous*) the male pos- 

 sesses the cementing apparatus, which homologically is 

 part of an ovarian tube modified. 



The individuals in every other genus (with the exception 

 of Scalpellum), in the several families, in the three Orders 

 of Cirripedia, are hermaphrodite or bisexual. Why, then, 

 is Ibla unisexual ; yet, becoming, in the most paradoxical 

 manner, from its earliest youth, essentially bisexual? 

 Would food have been deficient, and was the seizure of 

 infusoria by another and differently constructed individual, 

 necessary for the support of the male and female organs ? 

 The orifice of the sack of the female is unusually narrow ; 

 would the presence of testes and vesiculae seminales have 

 rendered her thorax and prosoma inconveniently thick ? 

 Seeing the analogous facts in the six, differently-con- 

 structed species of the allied genus Scalpellum, I infer 

 there must be some profounder and more mysterious 

 final cause. 



2. Ibla quadrivalvis. PL IV, fig. 9. 



Anatifa quadrivalvis. Cuvier. Mem. pour servir . . . Mollusq. 



1817, Art. Anatifa, Plate, figs. 15, 16. 

 Lbla cuvieriana. /. E. Gray. Annals of Philosophy, vol. x, 



New Series, Aug. 1825. 

 — J". K Gray. Spicilegia. Zoolog. Tab. iii, fig. 10. 



Tetralasmis hirstjtus. Cuvier. Regne Animal, vol. iii, 1830, 

 Anatifa hirsuta. Quoy et Gaimard. Voyage de l 5 Astrolabe, 



PL xciii, figa3. 7—10, 1834. 



* Certain plants offer a closer, though not perfect, analogy. Thus, in the 

 florets of some compositous flowers, the pistil, besides its proper female 

 functional end, serves to brush the pollen off the anthers ; while, in the florets 

 of some other compositse (see the account of Silphium in \ Ch. K. Sprengel 

 Das entdeckte Geheimniss der Natur'), the pistil is functionless for its 

 proper end, the flower being exclusively male, but its style is developed, 

 and still serves as a brush. So in the male Ibla, part of the ovaria, in a 

 modified condition, is still present, and serves as a cementing apparatus. 



