194 LANGDON. [Vol. XI. 



Methods. 



Sections stained with Kleinenberg's haematoxylin have been 

 used for a study of the finer structure of the sense-organs and 

 the course of the nerve-bundles passing to the epidermis. 

 The nerve-supply of the sense-organs and the course of the 

 nerve-fibres in the epidermis and in the central nervous system 

 have been studied by means of Golgi's shorter silver nitrate 

 method. The distribution of the sense-organs has been deter- 

 mined from surface views of the removed cuticula. 



The fact that these sense-organs of the epidermis have been 

 so often overlooked by competent observers seems to warrant 

 an account of the methods employed by me, although this 

 account contains little that is new. 



It is not difficult to obtain well stained sense-organs in a 

 good state of preservation, if sufficient care is taken in all 

 stages of the preparation. To insure successful cutting of sec- 

 tions, it has been found best to feed the worm on wood-pulp in 

 the preparation of which no chemicals have been used. In 

 killing, great care must be taken to avoid contortion or an 

 excessive discharge of mucus from the gland-cells of the epi- 

 dermis. The method found most successful is the alcohol 

 method given by Cerfontaine ('90), p. 337. But it has been 

 found best to have the alcohol act more slowly; 70% alcohol 

 was used in place of the 96% recommended by Cerfontaine, 

 and it was made to drop on the filter paper at the rate of sixty 

 drops a minute. In about an hour the worms are so stupefied 

 that all the paper may be removed except the small piece on 

 which the alcohol drops, and the alcohol may be made to drop 

 more rapidly. At the end of two hours the worms are placed 

 in 50% alcohol for an hour, in 70% for twenty-four hours — dur- 

 ing which this alcohol should be several times renewed — in 

 96% for twenty-four hours, and then preserved in fresh 

 96%. It is better to use for sections worms that have been 

 recently prepared. When these preserved worms are cut into 

 pieces, it is best to remove the wood-pulp from the alimentary 

 canal with small forceps in order to facilitate sectioning. Parts 

 of the worm chosen for study are run through absolute alco- 



