MOLLUSC A. 65 



Carry the cone of the mantle out straight, as in the 

 Squid (Fig. 55) ; turn the hinder end of the foot for- 

 ward, and bend the edges outwards until they meet, so 

 as to form the tube for ejecting water; enlarge the 

 eyes, making them lateral, and seated on the sides of 

 the head, as they are also in many Gasteropods ; pro- 

 duce parts around the mouth into numerous tentacles, 

 and the result is an image of the Squid. But in this 

 last transformation the mantle hollow, the gills, and the 

 opening of the intestine have shifted from the dorsal to 

 the ventral side. This has caused many naturalists to 

 suppose that the Cephalopod was really itself a re- 

 versed animal ; whereas the nervous system, the eyes, 

 the tongue, and intestine show that it is the mantle 

 hollow and accompanying organs which have shifted 

 place. 



In this coarse way we can show that the elements of 

 the structure are after all the same in all Molluscs ; but 

 here must be repeated the caution given in No. V. 

 These processes are not nature's processes ; they do 

 not show how she has modified animals, but how we 

 can explain by artificial means certain relations of 

 parts, certain homologies, and certain changes which 

 have taken place through the action of other and more 

 natural agencies. 



