one to show us how it was done. He first extracted the animal from 

 its shell, and then placed it in a medium sized test-tube which con- 

 tained a tablespoonful of caustic potash, which had become liquid by 

 the attraction of the moisture in the atmosphere. He next lighted 

 an alcohol lamp which made a good flame. Holding the test-tube 

 firmly between the thumb and fingers of the right hand, he held it 

 at the side of the flame, at the same time keeping the liquid in 

 motion by a rolling movement of the thumb and fingers. He let it 

 boil several times, being careful to avoid the boiling over of the animal 

 matter, as it would stick to the dry side of the tube. This hap- 

 pened once, but he shook the liquid over it and it again fell to the 

 bottom. 



After the animal matter was dissolved, he quickly poured the liquid 

 into a watch crystal, put a little clear water into the test-tube, shook 

 it up well, and poured it into another watch crystal. He then placed 

 the first watch crystal on a piece of white paper, and with the aid 

 of a large hand lens searched for the radula. The watch crystal was 

 given a gentle rotary motion, so that the solid particles in the liquid 

 might be brought to the center. " The minute radula will be known," 

 said the Professor, " by its long, curved form, and the little reticula- 

 tions on its surface. If it is not in the first crystal we must examine 

 the second. When it is found we will transfer it, with the fine 

 tweezers, to the glass slide, and mount it in Canada balsam, as we 

 did the radula of the large land snail. A much higher power of the 

 microscope will be necessary for studying this radula, as it is much 

 smaller. 



" If the teeth are very transparent it may be necessary to stain 

 them, and this may be done by putting the radula into a strong solu- 

 tion of chromic acid, which 

 colors it a yellowish brown. 

 It should be perfectly clean 

 before it is stained." 



Having shown us the 

 method of preparing the rad- 

 ula3 of small snails, Professor 

 Parker placed the prepared 

 slide of the radula of the snail 

 (a species of Amnicola) under 

 the microscope and bade us 

 look at it. This we did, and we saw that the teeth differed very 

 materially from those of either the land or fresh-water snails. The 



44 



Teeth of a water breather. Amnicola limosa. A, 

 central tooth; 1, 2, 3, lateral teeth. Greatly magni- 

 fied. (Stimpson.) 



