58 
to and removal of this special cause of growth and strength. 
Another conclusion seemed sketched on ,the surface of the exhibit 
that the abiding warmth of the day, carried beyond its coagent 
light, influenced the development on the N.W. by increasing its 
extension beyond that observed on the N.E., where the return of 
action commenced. Thus these natural coagents in life and health 
should not be separated in sanitation. 
Mr. J. Reid presented and explained five other exhibits from 
the same Pinetum. 
XT 
ON THE DENTAL APPARATUS OF THE 
HIGHER MOLLUSCA, 
BY 
MR. SIBERT SAUNDERS. ee, 
A general survey of the important division of the animal 
kingdom, comprehended under the term Mollusca, reveals a vast 
assemblage of animals possessing widely different forms, and — 
exhibiting in their structure many relative degrees of perfection. 
A closer scrutiny shows that the endowments and capabilities of 
the creatures are precisely those which are best suited to the con- 
ditions under which their life is to be passed ; and it follows that 
in those species which are sedentary (as is the case with most of 
the bivalve molluscs) the organization, although wonderful in its 
adaptation to the circumstances of the animal, is of a simple type 
compared with that found in those tribes which have the power of 
moving from place to place, searching for, and making selection of, 
their food. ‘ 
In these we find developments of structure suited to the 
requirements of the creature, and; the more active the habits of 
the animal, the more numerous and complete are the special organs 
with which it is furnished. Among the features thus developed 
in certain classes of this great sub-kingdom, none are more remark- 
able than the provision made for enabling the animal to securea 
supply of food. As has been already remarked, the bivalve 
mollusca, ¢.g., the oyster, cemented to a stone, or lying without 
power of. spontaneous movement in its ocean bed; the mussel, 
moored by its byssus.; the Pholas, self-immured in its rocky-cell ; 
_the Teredo, burrowing in concealment through a piece of timber, 
from which retreat is impossible, can never travel in search of food. 
