CHAPTER XIII. 

 "SHELL-FISH." 



ONE of the greatest hindrances to the unscientific, in the 

 way of a proper understanding of the true nature and relative 

 position of many forms of life, is to be found in our misuse of 

 words our poverty of language, which compels us to make 

 one word serve for quite dissimilar and unrelated things. 

 This unfortunate term, " Shell-fish," which we have felt com- 

 pelled to put at the head of this chapter, in place of the more 

 accurate " Bivalve Mollusks," is a case in point. I really want 

 a name that only includes these ; but in order to be strictly 

 popular in my chapter-heads, I must use this very general 

 term. Just now I turned to a popular and portable diction- 

 ary to see what was a familiar definition of the compound, 

 and I read there, " Shell-fish, testaceous mollusks," but even 

 for a popular explanation that does not go far enough, for 

 Shell-fish also includes crabs and lobsters, which are not 

 mollusks, but crustaceans. I daresay, too, that in a fishery 

 suit, if it served their purpose, lawyers would show plainly 

 that it embraced tortoises and turtles, which are chelonian 

 reptiles. We are all aware that in popular and legal language 

 everything that comes out of the sea is a fish, excepting the 

 coral-polyp which everybody, except naturalists, knows is an 

 insect ! 



What I really wish to make clear, after this little growl, is 

 that the present chapter will deal only with such creatures as 

 are (like oysters and cockles) sandwiched or boxed between 

 two valves or half-shells, and will not even glance at those 

 mollusks that are contented with a shell all in one piece ; 

 these are relegated to the next chapter. 



