220 



PTEROPODA. 



neck, and spread out on each side, in the substance of the wing, 

 forming an apparatus exactly comparable to the double-paddled 

 oar with which the Greenlander so dexterously steers his kajac or 

 canoe through the very seas inhabited by the little creatures we 

 are describing. We select as examples of this Order 



The Northern Clio (Clio borealis), an animal not more than an inch in length 

 (Fig. 235), but of truly marvellous structure. On each side of the mouth are three 

 conical appendages that to a superficial observer appear to be mere fleshy tentacula, 

 but in reality they are instruments of prehension of unparalleled beauty and astonishing 

 construction. Each of these six appendages, when examined with the naked eye, is of 

 a reddish tint ; but when examined under the microscope this colour is found to be 

 dependent upon the presence of numerous minute isolated rod specks, every one of 



FIG. 235. CYMBULIA AND CLIO. 



which, when still more highly magnified, is found to be a transparent cylinder resem- 

 bling the cell of a Sertularia, and containing within its cavity about twenty suckers 

 adapted to seize and hold minute prey : the number of these red specks is calculated 

 to be about three thousand ; so that there are at least (3000X20X6) 360,000 of these 

 microscopic suckers upon the head of one Clio an apparatus for prehension perhaps 

 unparalleled in the animal creation. When not in use, the appendages referred to are 

 withdrawn and concealed by two hood-like expansions that completely cover and pro- 

 tect the whole of this delicate mechanism. 



The Limacina helicina (Fig. 28) is another species found in company with the 

 above, in even still more innumerable hosts. It does not materially differ from the 

 Clio in its general structure, but its body is enclosed in a transparent spiral shell of ex- 



