are 



3^6 Studies A?iio7ig- Molhisks. [zoe 



I 



Family Bulimulidae membrane of Helix. 

 "Family Pupidae membrane of Helix. 



From all of these facts it will be seen that there are no invariable 

 characters or arrangements of these organs on which genera can be 

 based. They seem to be scattered throughout the class without 

 reference to divisions of any kind, and from these and other facts I 

 cannot resist the thought that genera, as we understand them at 

 present, do not exist in nature, and the sooner we abandon them for 

 some more natural divisions of these animals, the better it will be 

 for science and for the student. 



As the shell of a mollusk is extravascular, and moulded by the 

 mechanical action of the animal's mantle, and not by the pro- 

 cesses of secretion as bones and other parts of an animal's body 

 are formed, it (shell) does not constitute any portion of the an- 

 imal's body, but is simply an outside covering constructed by the 

 animal for the protection of its body. No animal can form or mould 

 part of Its own natural body. Its form, size and growth „.. 

 determmed by a principle inherent in the germ of all organic 

 bodies. Nor is any part of an animal's body extravascular. but 

 on the contrary all parts are closely connected with the 

 nous system, and whenever this connection is interrupted o.v- 

 ered or broken, the body withers, decays and disappears.' The 

 shell bears the same relation (mechanically) to the animal that 

 moulds and forms it that the web does to the spider, that spins 

 and sets it to catch insects for food. In both instances the mate- 

 rial is secreted by these creatures, and afterwards constructed into 

 the shell and web by mechanical action directed by the instinct 

 of these curious and skillful little mechanics. 



The_ shell of a mollusk then represents the instinctive impulses of 

 the animal, and nothing more. 



Besides the instinct common to all animals, viz: the reproduction 

 of their own kind, mollusks display in their shells instincts that are 

 regarded by man as evidence of a higher intelligence, and to the 

 philosophical student adds an importance and a charm to their 

 study not found, perhaps, in the study of some other branches of 

 natural history. 



For the purpose of study I separate these higher instinctive im- 

 pulses, as follows : 



ve- 



sev- 



