278 



ZOOLOGY. 



Besides this set of five cephalic ganglia, there are three pairs 

 of ganglia belonging to the visceral or sympathetic nerve, 

 which arise from the visceral ganglion situated among the 

 viscera ; a single one (the ventricular or splanchnic ganglion) 

 is situated over the stomach near the origin of the aorta, 

 which sends a nerve to the coecum, and another accompanies 

 the aorta ; the mate to this ganglion is situated near the 

 vena cava. A pair of ganglia is situated on the mantle walls 

 (ganglia stellata], and there are two branchial 

 ganglia. The kidneys (&) are irregular 

 branching spongy bodies, in intimate con- 

 nection with the auricles or branchial hearts. 

 The sexes are distinct. The ovary (o) is 

 large, especially when the eggs are ripe, and 

 is situated in the end of the body-cavity. 

 The single oviduct is as in some worms, 

 separate from the ovary, and in this respect 

 the Cephalopods approach or anticipate the 

 Vertebrates, in which the oviduct is also 

 separate from the ovary. The oviduct 

 (ov) is a thick straight tube, with a flaring, 

 deeply-lobed mouth. The eggs, when ex- 

 truded, are enveloped in ' a large gelatinous 

 capsule (Fig. 216), which is secreted by the 

 large flattened nidamental gland (c) on the 

 floor of the body-cavity, tied down at each 

 end by cord-like membranes. Usually there 

 are two nidamental glands. 



The earliest phase of development of the egg 

 of most Cephalopods (Sepia, Loligo} is like that of birds and 

 reptiles, the yolk undergoing partial segmentation, the blasto- 

 derm being restricted to a small disk, as in Vertebrates. Even- 

 tually the blastoderm encloses the whole yolk, the mantle 

 begins to form, the eyes are at first in-pushings of the outer 

 germ-layer, and the mouth appears. The digestive tract 

 originates from a primitive invagination of the outer germ- 

 layer (ectoderm), as in Amphioxus, Ascidians, worms, and 

 some Coelenterates. About the tenth day, as observed^ by 

 Ussow, at Naples, the gills, siphon or funnel, and arms arise, 



After Verrill. 



