196 LANGDON. [Vol. XI. 



are cut, the surrounding collodion is easily removed. When it 

 is desirable to use the oil-immersion on these sections, they 

 should be cut about lOyu. thick and the cover-glass pressed 

 down finnly. 



The following method was employed in the preparation of 

 the cuticula for a study of the distribution of the sense-organs. 

 A large worm which has been previously hardened in alcohol 

 is placed in 70%. Beginning at one end, the worm is cut into 

 pieces of 20 metameres each. As each piece is cut off it is 

 placed in 50% alcohol, a longitudinal cut is made with a sharp 

 razor through the body wall in the mid-ventral line, and the edges 

 of the cuticula along this cut are loosened with fine forceps. 

 Then by holding the cuticula firmly at one edge and gently 

 rolling the piece of the worm out from under it, the cuticula is 

 peeled off. All this is done under the 50%. The cuticula 

 usually is ready to peel off about as soon as the piece of the 

 earthworm is placed in the 50%. A glass slide is then held in 

 the alcohol, the cuticula floated onto it, and pressed down with 

 a camel's-hair brush ; the slide is removed from the alcohol, 

 and allowed to dry. No cover-glass or further preparation is 

 needed. With a little practice perfect preparations of the entire 

 cuticula may be thus made. Cerfontaine ('90) places the worm 

 in 30% alcohol for three or four days and removes the cuticula 

 entire, afterward cutting out pieces of it for study. This pro- 

 cedure is apt to macerate the cuticula, and the removal of the 

 latter entire renders more difficult the cutting of it into sections 

 for mounting. Cerfontaine says : " La structure de la cuticule 

 ne peut s'observer que sur des preparations fraiches, parce que 

 I'examen doit se faire dans I'eau ou, mieux encore, dans I'alcool." 

 Cuticula dried on the slide as described above has been found 

 to be in perfect condition for study over a year after prepara- 

 tion, and seems to show its structure better than when exam- 

 ined in water or alcohol. 



A Study of Haematoxylin Pi'eparatio7is of the Epidermis. 



General structure of the epidej'mis. — The epidermis of 

 Lumbricus agricola is covered exteriorly by a thin cuticula 

 composed of at least two layers of fibres ; the fibres of one layer 



