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 vesiculæ seminales have rendered her thorax and prosoma inconveniently thick? Seeing the analogous facts in the six, differently-constructed 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.]
![[Pl. IV]](#475865927904411783_p04.png.id-6472061628846608008.wrap-0.html.html){kind=link}
![[fig. 9.]](#475865927904411783_p04f9.png.id-7671354820623789315.wrap-0.html.html){kind=link}
Anatifa quadrivalvis. Cuvier. Mém. pour servir ... Mollusq. 1817, Art. Anatifa, Plate, figs. 15, 16.
Ibla cuvieriana. J. E. Gray. Annals of Philosophy, vol. x, New Series, Aug. 1825.
—— ————— J. E. Gray. Spicilegia. Zoolog. Tab. iii, fig. 10.
Tetralasmis hirsutus. Cuvier. Regne Animal, vol. iii, 1830.
Anatifa hirsuta. Quoy et Gaimard. Voyage de l’Astrolabe, Pl. xciii, figæ. 7-10, 1834.
I. (Herm.), valvis et pedunculi spinis sub-flavis: basali tergorum angulo, introrsùm spectanti, hebete, quia margo carinalis inferior longiùs quam margo scutalis prominet.
Hermaph.—Valves and spines on the peduncle yellowish: basal angle of the terga, viewed internally, blunt, owing to the lower carinal margin being more protuberant than the scutal margin.