GASTEROrODA. 91 



extracted from their shells by drawing them out with a mounted 

 needle or hook, and in the larger species the head is cut off, and 

 the remainder of the animal rejected. In the minute species, the 

 shell may be removed by hydrochloric acid. Either process may 

 be employed, to equal advantage, upon shells which contain the 

 dried remains of the animals. 



The specimens are then placed in a small porcelain crucible 

 containing water, in a sand bath over a Bunsen burner. A little 

 boiling will soon render them in a condition for the rapid action 

 of a small piece of caustic potash, Avhich is next placed in the 

 crucible, and the whole allowed to boil until the tissues have 

 become disintegrated and partially combined with the potash. 

 I'he action of the potash should not be continued after it has 

 completed its work upon the tissues, as continued boiling will 

 attack the thin membrane, upon which are situated the lingual 

 teeth, and which holds them in position. 



After removal from the burner, water is added and the undis- 

 solved material allowed to precipitate. With a pipette having a 

 rubber bulb, or by decanting, the fluid is nearly all removed, and 

 clean water again added. This is repeated, until the potash and 

 light flocculent matter are eliminated. 



The residue is then washed into a flat-bottomed dish, or large 

 watch crystal, and the radulae, in the majority of cases, can be 

 perceived by the unassisted eye, and removed, by means of fine, 

 mounted needles, to another receptacle containing a very small 

 amount of water. In case the radul^e are very small, the material 

 is transferred drop by drop, with a pipette, and examined, under a 

 one inch or three-quarter inch objective, on the horizontal stage 

 of a microscope, preferably furnished with an erector. They can 

 then be removed from the mass of extraneous matter, and placed 

 in a separate receptacle, as in the former instance. 



A drop of strong chromic acid is added to the specimens, and 

 in from one to two minutes the teeth on the radulre are stained a 

 light yellow or amber colour. After washing out the chromic acid, 

 the specimens are dehydrated in the usual way, and after removing 

 the alcohol with a pipette, absorbent paper, and partial evapo- 

 ration, oil of cloves is added, and the specimens are ready for 

 mounting in Canada balsam. 



