264 ^^^- t^^""" ^"• 



Methods of Work. 



In studying the living worm, it was found to be of great advan- 

 tage to slightly compress it under a cover-glass supported by 

 wax feet. Intravitam stains were found to be of great value in 

 marking out different histological elements of the living worm. 

 Bismarck brown stains the rods in the integument, and them 

 only. Methylin blue stains the pharyngeal cells, and dahlia 

 stains the brain. Details as to methods of using the stains will 

 be given under the organs referred to. 



Macerations were found to be a great help in many cases. I 

 obtained the best results by fixing the worms in i per cent osmic 

 acid for four minutes and then leaving them in i per cent acetic 

 acid for forty-eight hours. They were then placed in a solution 

 consisting of one part glycerine and one part Deal's carmine for 

 twelve hours. When a worm was placed under a cover-glass in 

 this solution, and the cover-glass slightly tapped, the histological 

 elements separated very easily and the nuclei were found to be 

 well stained. 



For sections, worms were fixed in both hot and cold corrosive 

 sublimate, chrom-osmic-acetic acid, i per cent osmic acid, 33 

 per cent formic acid, and Perenyi's fluid. Of these fixing agents 

 chrom-osmic-acetic acid was the most satisfactory. It killed 

 the worms before they were distorted, and before any of their 

 parts were in any way broken up. 



For staining, alum carmine, hsematoxylin, and gold chloride 

 gave the most satisfactory results. Kolliker's ('90) silver nitrate 

 method was used with excellent results as a nerve fibre stain. 



Anatomy and Histology. 

 Integument. 



My observations on the structure and arrangement of the 

 different elements of the integument agree with those of earlier 

 observers, — except as to the arrangement of the circular and 

 longitudinal muscle fibres. 



Graff ('82, p. 65) says that the circular fibres of the muscular 

 layer of all Rhabdocoels lie next to the epithelial cells, except in 

 Microstoma litieare, where the longitudinal fibres lie next to the 



