LEWIS. 



POLYCH^TE ANNELIDS. 249 



After the presence of these sense organs had been established and 

 their finer structure studied by the methods described, I was able to apply 

 successfully the methyleu blue method to living material. The results 

 thus obtained confirmed what had already been found, and gave some 

 additional facts. The methylen blue was used in the following manner. 

 The worms were first narcotized with chloroform and then a 1.5% solu- 

 tion of methyleu blue in normal salt solution (0.66%) was injected into 

 the body cavity, the injection often being made in two or more regions 

 of the body. The worm was then put back into sea water. After a few 

 minutes a second injection, similar to the first, was made, and the worm 

 was again returned to the sea water. In the course of five or six houi's 

 the sense organs gave evidence of being stained. The worms were then 

 placed in Bethe's ('96) mixture for invertebrates to fix the blue, after- 

 wards deliydrated in alcohol, embedded in parafiine, and cut into sections 

 as thick as practicable. Griibler's B. X. brand of methylen blue proved 

 to be the most satisfactory. The results obtained by the methylen blue 

 method will be considered later. I will pass now to the consideration of 

 the sense organs. 



3. Distribution of Sense Organs. 



Both Axiothea torquata and Clymene producta have two well marked 

 body regions, separated from each other by a sort of collar. These two 

 regions I call thoracic «ind abdominal, using the terms employed by 

 Eisig for the body parts of the CapitellidcE. The distribution of the 

 epidermal sense organs over these regions is as follows. (See Plate 8, 

 Fig. 68.) 



a. In the Thoracic Region. 



The thoracic region consists in both genera of the first four segments. 

 The posterior part of the buccal segment and the anterior portion 

 of the one next following show a peculiar mosaic arrangement of the 

 surface not found in any other portion of the worm. The mosaic-like 

 patches are bounded by irregular linear grooves, and their surface is 

 slightly raised. Upon these patches the sense organs (represented in 

 Fig. 68 by dots) are found in abundance. In the grooves both sense 

 organs and gland pores are wanting. It is evident that the sense 

 organs, being situated upon these patches, are more exposed to contact 

 from without than they would be if they were located in the grooves. 



The proboscis is longitudinally ribbed, and the sense organs upon it 

 show a corresponding arrangement, for they are found upon the longitu- 

 dinal ridges, not in the grooves. 



