b EAMBLES IN SEARCH OF SHELLS. 



grass ; and Pupa umhilicata, Clausilia rugosa, and 

 Bulimus ohscunis bury their heads only to increase 

 their shells. "With respect to Zonites cellariusf 

 Z. nitidus, and Z. nitidulus, it was not satisfactorily 

 ascertained whether their heads were buried during 

 the process of growth or not. 



We are all tolerably familiar with the fact that 

 one essential character of the vertebrated animals is 

 their possession of a brain and spinal cord, from 

 which proceed those 



" Tracts along which the mysterious will 

 Is conveyed, by a process on which Fancy lingers 

 With awe, from the brain to the tips of the fingers," 



or their analogues, and other portions of the animal 

 frame. In the species under consideration this plan 

 is considerably modified, and instead of one cerebral 

 mass supplying the whole system, we find half a 

 dozen ganglionic centres from which the nervous 

 threads radiate to the organs of sight, smell, hear- 

 ing, and touch (which appear to be well developed), 

 and the important systems of digestion, circulation, 

 respiration, locomotion, and reproduction. 



Respiration in the animals of this class is carried 

 on by means of a rudimentary lung in each member 



