OF MICROSCOPIC OBJECTS. 17P 
“ As to preserving the animals till wanted, they should 
simply be dropped alive into glycerine or alcohol. Glycerine 
is perhaps best where only the tongues are wanted ; but it 
leaves the animals very soft; and as it does not harden 
their mucus at all, they are very slippery and difficult to 
work upon when so preserved. 
“Then as to the apparatus required for dissection. In the 
first place, all the work is to be done under water, and a 
common saucer is generally the most convenient vessel 
to use. No kind of fastening down or pinning out of the 
animal is needed; and, in fact, it is much better to have 
it quite free, that you may turn it about any way you wish. 
The necessary instruments are a needle-point, a pair of 
fine-pointed scissors, and small forceps; the forceps should 
have their points slightly turned in towards each other. 
« A word or two on the lingual apparatus generally, and 
on its special characters in # few different animals, will con- 
clude what I have to say. 
“The mode of using the tongue can be easily seen in any 
of the common water-snails, when they are crawling on the 
glass sides of an aquarium; it may then be observed that 
from between the fleshy lips a thick mass is protruded, with 
a motion forwards and upwards, and afterwards withdrawn,, 
these movements being almost continually repeated. The 
action has the appearance of licking; but when the light 
falls suitably on the protruded structure, it is seen to be 
armed with a number of bright points, which are the lingual 
teeth, so arranged as to give the organ the character and 
action of a rasp. 
“Tf you proceed to dissection, and open the head of one 
of these mollusca (say, for instance, a common limpet), you 
will find the cavity of the mouth almost filled with the thick 
fleshy mass, the front of which is protruded in the act of 
feeding; and on its upper surface, extending along the 
middle line from back to front, is seen the strong membranous 
band upon which the teeth are set. The mass itself consists 
of a cartilaginous frame, surrounded by strong muscles ; and: 
