248 PROCEEDINGS OF THE AMERICAN ACADEMY. 



was removed entire for surface study ; (2) sections, prepared either from 

 material fixed in corrosive sublimate and stained with hsematoxylin, or 

 such as had been fixed in vom Rath's picro-osmic-acetic-platinic chloride 

 mixture ; (3) methylen blue employed upon living tissue, which was after- 

 wards fixed, hardened, and sectioned. 



For removing the cuticula the following procedure was found most 

 successful. The worm was first narcotized in a mixture containinsf 95 

 volumes of sea water and 5 volumes of 95 % alcohol, and then placed for 

 a time, varying from 24 to 48 hours, in a lOoL solution of sodium chlo- 

 ride. It was next removed to fresh water, and an incision through the 

 cuticula of the back made with the points of scissors. The incision was 

 carried along the whole dorsal line of the animal. A little shaking in 

 the water with the forceps, aided with the scalpel, is sufficient to remove 

 the cuticula entire, although it is usually most convenient first to cut the 

 worms into pieces. The portions of cuticula thus obtained were floated 

 upon slides ; part of the water was drained off, and the rest allowed to 

 evaporate. It is possible in this way to make permanent preparations of 

 the cuticula. If the worm has been left in the salt solution a sufficient 

 time, all the epidermal cells will remain behind, and a preparation of per- 

 fectly clean cuticula will be obtained. From such preparations the dis- 

 tribution of the sense organs could be determined easily by the use of 

 low powers of the microscope. Preparations of this kind were also 

 valuable for determining the presence and number of the canals serving for 

 the passage of sensory hairs, and for comparing the sizes of the different 

 sense organs. 



Another method of maceration which was found fairly successful, 

 although in general inferior to the one just described, was the use of a 1 % 

 solution of potassic bichromate. After the worm had been left in this 

 solution for several weeks, fairly large pieces of cuticula could be 

 removed. 



For the study of the finer structure of the sense organs, material pre- 

 pared by the vom Rath method gave the most satisfactory results. By 

 this method, sense hairs and cuticula, as well as the cells of the epidermis, 

 were well preserved. It was found to be important to use great care in 

 narcotizing the worms before placing them in the killing fluid, for other- 

 wise the sense organs are contracted so as to be worthless. 



Sections from material fixed in mercuric chloride and stained with 

 haematoxylin showed plainly the presence of the organs and the peculiar 

 condition of the cuticula above them ; but the sense hairs were matted 

 together, and in other respects the preparations were inferior to those 

 prepared by the vom Rath method. 



