206 THE ORGANIZATION 



and the oviduct, (ov 1 ,) i. e., the canal through which the eggs 

 pass to the outer world, extends in variously convoluted folds to 

 a point near the right side of the head, where it opens (o) to give 

 egress to its contents. Not far behind the outlet of the oviduct, 

 a tubular blind-sac (ma) opens into the latter. It serves as a 

 reservoir for the fertilizing fluid which is poured over the eggs 

 as they pass along the oviduct (ov } ) toward its aperture. 



If now we compare the relative position of these organs with 

 that in the Oyster, (fig. 121,) we shall find that whereas in the 

 latter the bulk of the organization is, as it were, pushed over to 

 the left side, in the Helix it is reversed in this respect, and is 

 enclosed entirely in a deep spiral shell, which corresponds to the 

 right valve of the oyster. There is no left valve in the Helix, but 

 in other Gasteropods it exists in the form of a horny, or shelly, 

 flat, spirally marked shell, which is attached to the back of the 

 creeping disc, near its posterior end. When the animal with- 

 draws into its shell, this valve, the operculum, fits the aperture 

 closely, and protects the body from all intruders. The most 

 noteworthy features in Gasteropoda, as represented by Helix, 

 are the head-like configuration of the anterior end, and the great 

 preponderance of the nervous ganglia in that region. These 

 characteristics we find carried to a much higher degree in the 

 Cephalopoda, the highest order of Mollusca. 



m e tfl f I otj Iv an po hv l in A 1 v a aoi me fn 



t hd g l op th ao n gl th l pv l ao 2 pa h sk st ov hv sfti 



Fig. 124. 



Fig. 124. Loligopsis il/ecebrosa. Les. | of natural size. A profile view of 

 the left side of a Squid. t, the eight shorter arms; f 1 , the pair of longer arms; 

 hd, the head ; fn, the fin ; f, the funnel ; I, the edge of the mantle ; me, the 

 cavity of the mantle; sh, the shell; sh 1 , the conical hollow of sh ; m, the jaws ; 

 th, th), the throat; st, the first stomach or crop; in, the intestine; an, the pos- 

 terior end of the intestine; Iv, the liver; h, the auricle of the heart; h l , the 

 ventricle of the heart ; ao, ao 2 , the aorta which carries the blood forward ; ao 1 , 



