SENSORY AND GLANDULAR EPIDERMAL ORGANS 

 IN PHASCOLOSOMA GOULDII. 



MARGARET LEWIS NICKERSON. 



During the summer of 1897, while enjoying the advantages 

 of the Marine Biological Laboratory at Woods Holl, Mass., I 

 had an opportunity to apply the methylene-blue intra vitam 

 nerve stain to a study of the epidermal organs of the Gephy- 

 rean worm Phascolosoma Gouldii. This form lends itself well 

 to this method of study, as the tough body wall is not easily 

 torn in the process of injection, and the copious body fluid 

 surging back and forth quickly carries the injected stain to 

 all parts of the peritoneal cavity. The use of methylene blue 

 gave as results some facts regarding the peripheral nervous 

 system which could probably not be obtained in any other way. 

 These were supplemented and confirmed, as far as possible, by 

 maceration preparations and by sections prepared by the ordi- 

 nary histological methods, as well as by the picro-osmic-acetic- 

 platinic chloride method of Vom Rath ('95), This latter method 

 was found to be especially useful in the study of glandular 

 structures. 



A brief description of the structure of the body wall will be 

 given, not with the idea of presenting anything new, for the 

 general anatomy of the worm is well known (Andrews, '90), but 

 for the purpose of making clearer my account of the epidermal 

 organs. 



The body wall consists of three parts : the cuticula, the epi- 

 dermis, and the muscular layers. In the regions of the probos- 

 cis and of the tail the cuticula is thrown into elevations or 

 papillae, but in the middle region of the body it forms a com- 

 paratively smooth covering. If the cuticula from this middle 

 region is studied in sections, it will be seen to show numerous 

 large excavations upon its inner surface. The epidermis, which 

 consists of a single layer of columnar epithelial cells resting 



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