PHYLUM MOLLUSCA 



267 



I... 



TV' 



Jia.c 



opy 



which enters the mantle cavity flows over them, supplying oxy- 

 gen to the blood and carrying away carbon dioxide. 



The two nephridia or kidneys (Fig. 192, Ne) are white trian- 

 gular bodies extending forward from the region of the branchial 

 hearts and opening on either side of the intestine at the ends of 

 small papillae. 



The nervous system consists of a number of ganglia mostly in 

 the head. The principal ones are the supra-cesophageal, in- 

 fra- cesophageal, suprabuccal, infrabuccal, 

 stellate, and optic ganglia. 



The sensory organs are two very highly 

 developed eyes, two sl-atocysis, and prob- 

 ably an olfactory organ. The statocysls 

 are two vesicles lying side by side in the 

 head ; each contains a concretion, the 

 statolith, and is probably an organ of 

 equilibrium. The eyes (Fig. 192, E ; 



Fig. 193) are large and somewhat similar FIQ I03 ._ Diagram of 

 superficially to those of vertebrates (com- the eye of a squid, Loliw, 



-r^. -,, -i^- T 4- u i i a. o.c, anterior optic chain- 



pare Fig. 193 with Fig. 351). Just behind ber; - ^ cornea < .,. iris . 



the eye is a fold which projects back- J, lens; Z', external portion 

 ward under the collar, and is probably .*'> '/^ p c 8t X 



olfactory. optic chamber; r, retina. 



. , .,, r 



Squids are either male or female. 

 reproductive organs (Fig. 192, Go] of the Grenadier.) 

 male are the testis, a vas Jcfcrcns, a 



spermatopl/oric sac, which contains sperms bound together into 

 bundles called spermatophores, and a copulatory organ, the penis. 

 The female organs are an ovary, oviduct, omducal gland, and 

 nidamental gland. 



b. Cephalopoda in General 



Classification. - - The CEPHALOPODA may be divided into two 

 orders according to the number of gills, kidneys, and auricles, 

 and the character of the shell. 



rpi (From the CambrM: . 



The Natural History> aftcr 



