MUSEUM OF COMPARATIVE ZOOLOGY. 7 



traced only on cleared specimens in which the intestine contained dark- 

 colored food matter. For staining, Grenadier's alcoholic borax carmine 

 followed by differentiation with acid alcohol proved to be the most use- 

 ful and reliable method. I have stained both in toto and on the slide. 

 Good sections for topographical study were obtained by staining in 

 alcoholic borax carmine for 24 hours and cutting in the horizontal plane 

 sections 30 fx. in thickness. By thus lightly staining, the nerve tissue 

 takes none of the color, and in such comparatively thick sections the 

 finer branches show as white lines against a red background. Orth's 

 picrocarminate of lithium is a valuable reagent on account of the select- 

 ive action of the picric acid for all glandular tissue, which it brings 

 out in sharp contrast to the red color of the other tissues. I have used 

 this reagent also with excellent results for macerating. The affinity of 

 hematoxylin stains for formed substances renders them of little use ; 

 their intense reaction with the great number of glandular structures tends 

 to obscure results. For isolation preparations, the best results were 

 obtained by macerating directly in the stain. I also used successfully 

 the osmic-acetic method of maceration on fresh material. The isolated 

 living pharynges were killed in hot \oJ silver nitrate for the purpose of 

 demonstrating the epithelium. Depigmenting was accomplished by the 

 use of a 1 of solution of potassic hydrate which was allowed to act for a 

 few minutes on sections fixed to the slide with Schallibaum's clove-oil 

 collodion fixative. 



Cilia are present over the whole surface of the animal. In material 

 that had been prepared in hot corrosive sublimate, the middle region of 

 the ventral surface, where the hypodermis is thinnest, was often desti- 

 tute of cilia. Likewise at the lateral edges they may be wanting. 

 These conditions are, however, due to the action of the reagent, since in 

 the living animal cilia are always present in these places. At the ante- 

 rior end of the body on either side of the head, the cilia are somewhat 

 longer than elsewhere. They attain their greatest length at that por- 

 tion of the margin of the head which forms the auriculate projections. 

 From the middle of each projection they gradually diminish in length 

 until, at the anterior tip of the body and at an equally distant point 

 behind the auricles, they are reduced to the normal length. These two 

 areas covered by the longer cilia probably correspond to the " Tastor- 

 gane" of Iijima ('84, p. 366), and are directly related to local modifi- 

 cations of the hypodermis. 



1 cannot find either the short immovable hairs or the long " Geissel- 



