Proceedings 79 
involves the cutting of many sections; with regard to which I 
should like to say, in order to save the time of others who may 
be embarking in this direction, that a good microtome and a 
good incubator are sources of perpetual pleasure, while the reverse 
is true of rudimentary or superannuated appliances, 
The sectioning method is also requisitioned for the general 
study of the anatomy of snails. Hitherto most of the work has 
been done by dissecting, with or without the aid of a magnifying 
glass or erecting microscope. But the time has come for the re- 
sults so obtained to be checked by special sections of material 
properly fixed and afterwards properly stained. The histology 
of the snail is as yet very imperfectly known. But the following 
facts are known, and may be worked in with Hyatt’s valuable ob- 
servation; the different species have constituent cells and cellular 
organs of widely varying dimensions. This variation is not always 
proportionate to the bulk of the animal. (For example, the ra- 
dula in a large species is not so much larger, and in a small 
species not so much smaller, than would have been expected from 
comparison with a medium-sized species). It is found that cer- 
tain sorts of cells vary according to circumstances much more 
readily than others do. Consequently every variation in size 
necessarily implies a variation in the form and symmetry of the 
animal, viewed as a whole. This principle is worth further work- 
ing out, since the fact of the immense amount of variation in 
form is one of the most difficult of the problems connected with 
evolution. And in order that it may be worked out, a precise 
knowledge of snail histology is needed. 
These few observations, which I have been obliged to condense 
as much as possible, will, I think, satisfy you that snail collecting 
isa pursuit which may lead to important and interesting develope- 
ments. Within the last quarter of a century the instruments of 
research—the microscope, the microtome and the camera, have 
been improved almost beyond recognition; and the most effective 
means of using them are now known. We now insist upon know- 
ing the reasons why we employ different processes, instead of 
trusting to tradition and rule-of-thumb. 
Time was, when snails were collected for ornament; and 
pearls are still valued for a mixtue of financial and aesthetic 
