DICYEMIDAE.—If the kidney of _Eledone moschata_, a Cephalopod common on our south-western shores, be opened, a number of fine, yellowish, hair-like filaments may be seen attached at one end to its inner surface, floating in the fluid contained in the renal cavity. These may be _Dicyemennea eledones_ Wag., although another form, _Dicyema moschatum_ Whit., also occurs in the same host. _D. eledones_ (Fig. 46) is 7 to 9 mm. long, transparent, and is composed of one large inner cell with a simple nucleus (Fig. 46, _n.end_), and of an outer layer of ciliated cells, nine of which form the "calotte" or pole by which the animal is attached. Within the former (endodermal) cell the formation of urn-shaped "infusoriform embryos" takes place (B and C), the fate of which is not known, but they are possibly the males. The individual which produces these larvae is called a {94}"Rhombogen." Other individuals which produce a more elongated larva ("vermiform larva," Fig. 45) are called "Nematogens," and Whitman has described a third kind, which produce first infusoriform, and then vermiform, larvae (Secondary Nematogens).[113] The occurrence of the known species of Dicyemids (a group which has not been investigated on our coasts) is as follows:— Species. Host. _Dicyema typus_ van Ben. _Octopus vulgaris._ _D. clausianum_ van Ben. _O. macropus._ _D. microcephalum_ Whit. _O. de Filippi._ _D. moschatum_ Whit. _Eledone moschata._ _D. macrocephalum_ van Ben. _Sepiola rondeletii._ _D. truncatum_ Whit. _Rossia macrosoma_, _Sepia elegans_, _S. officinalis._ _D. schultzianum_ van Ben. _S. biseralis, Octopus vulgaris._ _Dicyemennea eledones_ Wag. _Eledone moschata, E. aldrovandi._ _D. mülleri_ Clap. _E. cirrosa._ _D. gracile_ Wag. _Sepia officinalis._ _Conocyema polymorphum_ van Ben. _S. officinalis, Octopus vulgaris._