CEPHALOPODA. 



447 



is formed upon the body. These ridges (s. s.) represent the epipodium ; their 

 anterior ends are continuous and attached, the posterior ends are at first free 

 but eventually uniting, they form the funnel (D.^.j. The rudimentary gills 

 {b.) appear between the epipodium and mantle. The alimentary canal is at 

 first straight ; (the mouth being at a, the vent at b, in Fig. 229, A.) 



" The embryo now grows faster in a vertical than in a longitudinal direc- 

 tion, so that it takes on the cephalopodic form. The intestine as a conse- 

 quence, becomes bent upon itself; and the anterior pairs of arms gr.jw over 

 in front of the head and unite, so as eventually to throw^ the mouth nearly 

 into the centre of the arms." {Huxley.) 



At a later period of development (Fig. D.) 

 the respiratory movements are performed by 

 the alternate dilatation and contraction of the 

 mantle ; and the ink-bag is conspicuous by the 

 colour of its contents, which are sufficient to 

 blacken a considerable quantity of water. At 

 the period of exclusion from the uidamental 

 capsule, five layers of the sheU of the young 

 cuttlefish have been formed; but except the 

 nucleus, which is calcified, they are horny and 

 transparent. The lateral fins are broader than 

 in the mature animal. 



The observations of Madame Power respec- 

 ting the young Argonaut, (quoted at p. 66), 

 must have been made on the Hedocotylus. 

 The embryo as described by KoUiker has simple, 

 coiiiciil arms (1—4) ; and the elements of 

 the funnel appear as a ridge {f) on each side of the body. In Fig. 230, 

 y, is the yolk-sac ; o, the position of the future mouth ; e, the eye ; b, the 

 gill ; m, mantle. 



Octopoda, p. 65.— The account already given of the extraordinary 

 condition of the male of the Argonaut and some other octopods has since been 

 modified and extended by the observations of Dr. H. Muller* and M. Verany.t 



According to Dr. Miiller, the Hectocotyle of the Argonaut is an arm 

 irregularly metamorphosed, spontaneously detached, (when the fluid formed 

 in the true testis has been deposited in it,) enjoying an independent life, feed- 

 ing on the female Argonaut, and fecundating by a true union. 



The perfect male Argonauts are one inch in total length, and shell-less, 

 (like the females of that size) ; their dorsal arms are pointed, not expanded. 

 The testis is very large, and like that of the Octopus in structure 



Fig. 230. Argonaut, 

 embryo in the e^Q. 



* Annales des Sciences Naturelles, t. 16, No. 3, and An. Nat. Kist., June, 1852. 

 t Moll. Medit. 4° Genes. 1851. An. Sc. Nat. t. 16, 1852. 



