DICECIOUS MOLLUSCA. 361 



pends the ovigerous capsules from its float ! From the 

 float ? Yes* — the snail is taught to fix its ovigerous cap- 

 sules, which are sometimes numerous, to the under side of 

 the " float," where they are suspended by little pedicles in 

 a line, or after a pattern peculiar to each species. It is said 

 that the mother then detaches the float loaded w r ith its 

 teeming burden ; and suspended, in this way, near the sur- 

 face, the embryo young receive the influence of the life- 

 giving air, and are matured ; and thus the race is preserved 

 and multiplied. f Here you have the pretty fable of the 

 Halcyons almost realised ; and in your reflections on the 

 real you may arrive at the old conclusion, that " Heroum 

 fabula veris vincitur historiis." 



All the Cephalopods belong to the dioecious section of 

 mollusca, and the sexes of at least many species are distin- 

 guishable by a marked difference in the form of the body. 

 Risso says that the body of the male Octopus is more conical 

 than that of the female ;J and the distinction is still more 

 marked in the Loligines. The male of Loligo subulata has 

 the extremity of the body prolonged behind by a fleshy tail 

 a half longer than the female ; and as this dissimilarity ex- 

 tends to the cartilaginous pen or back-bone, a naturalist 

 ignorant of the sexual distinction might be led to mistake 

 the sexes for distinct species. § The males of the Octopus 

 are also less numerous than the females in the proportion, 

 as estimated by Cuvier, of about five to one;|| but the 

 grounds oil which the estimate is founded are uncertain, 

 nor can it be safely applied to the other genera of Cepha- 

 lopods. 



The Cephalopods are, without any exception, oviparous ; 



* A fact first ascertained by Sir Joseph Banks : — " We also took several 

 of the shell-fishes, or testaceous animals, which are always found floating on 

 the water, particularly the Helix ianthina and violacea ; they are about the 

 size of a snail, and are supported upon the surface of the water by a small 

 cluster of bubbles, which are filled with air, and consist of a tenacious slimy 

 substance that will not easily part with its contents. The animal is ovi- 

 parous, and these bubbles serve also as a nidus for its eggs." — Sir Joseph 

 Banks, in Kerr's Collect, of Voyages and Travels, vol. xii. p. 370. edit. 1824. 



t Rang's Manuel, 197,'pl. 5, fig. 3. Zool. Journ. iii. 265. Mrs. Gray's 

 Fig. Moll. Anim. i. pi. 48. Sir Everard Home has published a beautiful 

 figure of the shell of an Ianthina covered with a much twisted and beaded 

 filament formed by a long series of membranous capsules or cells, each cc-11 

 enclosing a single ovum. This Sir Everard unhesitatingly (yet erroneously) 

 describes as the "camcrated nidus" of the Ianthina. — Comp. Anat. iii. p. 

 398, and iv. pi. 141. 



% L'Europ. Mcrid. iv. 5. 



§ Ann. des Sc. Nat. (1842) xviii. 259. 



II Mem. i. 31. 



