6 Journal of Comparative Neurology. 



served in methylene blue preparations ; in Nereis I have always found 

 it very well preserved and its structure, especially after the use of the 

 secondary stain, clearly defined. 



The removal of the cuticula of Nereis virens, owing partly to its 

 greater thickness and partly to the fact that it is more firmly attached 

 to interior structures, is much more difficult than in Lumbricus. The 

 alcoholic method used with the latter form (Langdon '95) was a total 

 failure when tried on Nereis. Macerating in Miiller's fluid for three 

 months gave better results, but my best results were obtained with 

 a 10% salt solution, suggested to me by Miss Margaret Lewis (see 

 Lewis, '98). I found it best to prepare the cuticula as follows: The 

 worms were killed in the 10% salt solution and left for a few days in a 

 small quantity of this fluid. They were then washed thoroughly in 

 plenty of distilled water to remove all trace of the salt, and placed in 

 35% alcohol to render the cuticula firmer. Each worm was then slit 

 its entire length close to the parapodia of one side, all the parapodia 

 of the other side were cut off, and the body wall cut through along the 

 anterior margin of the buccal cavity. The greater part of the interior 

 tissues were removed with fine forceps and the inside of the cuticula 

 brushed clean. It was found difficult to get all the tissues out of the 

 cephalic cirri. All could be removed from the palps and tentacles and 

 some from the cirri by turning the structures inside out with a pipette, 

 brushing the inner surface, and then turning them back again by the 

 action of the pipette on the opposite surface. When it was desired to 

 mount the cuticula of a given parapodium, the latter, while still at- 

 tached to the body cuticula, was turned wrong side out, cleaned, 

 turned back again, and then cut off and mounted separately. After 

 being thoroughly rinsed in clean 35% alcohol, the cuticula was cut into 

 convenient lengths, floated onto a slide, pressed down with a brush, 

 and then allowed to dry. The cuticula of the caudal region macerates 

 so quickly that it is best to cut off this region and mount its cuticula 

 after it has been in the salt solution a shorter time than that allowed for 

 the rest of the body. 



For making a chart to show the distribution of the sense-organs 

 by means of the cuticula, a Zeiss projection microscope fitted with an 

 arc-light was used ; it was found that the image of the cuticula was 

 more distinct when the room was not darkened. The distribution of 

 of the organs in the various sensory appendages was also studied by 

 means of surface views of living appendages taken from worms that 

 had been injected with the methylene blue. In such appendages the 



