OPPENIIEIMER. RHYNCHOBOLUS DIBRANCHIATUS. 555 



the subcuticular tissue of the sheath of the proboscis, with which, more- 

 over, it is evidently continuous. This tissue . . . consists of a fibrous 

 network, in the meshes of which lie ganglion cells." Further on (p. 696) 

 he says : " The ganglion cells between the leaves of these ' Hautlappen ' 

 lie in a single layer and are surrounded by strands of fibres, so that they 

 lie as it were in the meshes of such a net made up of bundles of fibres ; 

 however, it seems to me very doubtful whether these strands of fibres 

 which make the meshes are all of nervous nature ; on the contrary I 

 believe that the greater mass of this fibrous tissue is identical with that 

 which lies under the chitinous cuticula of the ' Russelrohre ' and forms 

 the sheath of the longitudinal nerves." 



If I understand Ehlers correctly (he has no figures showing these 

 histological conditions), I do not entirely agree with him concerning the 

 structure of the " Lappen." Within the peritoneum I find connective 

 tissue, ganglion cells, and also cells not mentioned by Ehlers (PI. 2, 

 Figs. 7, 8). These last have an epithelial character; they form, indeed, 

 the main bulk of the lobe, as appears both in material prepared in the 

 vom Rath mixture and in two haematoxylin preparations made from 

 material fixed respectively in corrosive sublimate and in sublimate- 

 acetic. The " Fasergewebe " of Ehlers I consider nervous in large 

 part. Almost all of the fibres (Fig. 8) surround, not the ganglion cell, 

 as one might infer from his description, but its nucleus, and pass out at 

 one pole of the cell body to the longitudinal nerves of the proboscis. 



Finally, nerve fibres from the longitudinal nerves and from the pe- 

 ripheral nerve plexus can be traced out peripherally into the small papil- 

 lae which are thickly distributed over the surface of the " Russelrohre." 



Through the kindness of Mrs. Margaret Lewis Nickerson, who sug- 

 gested to me the subject of the present paper, I was able to begin my 

 study of the distribution of the sensory papillae of the proboscis on a 

 preparation of the cuticula already made by her. The cuticula had been 

 prepared by a method which was first employed by Mrs. Nickerson. 

 All my subsequent preparations of the cuticula of other individuals were 

 secured by the same method, which was as follows: The worm, after 

 being narcotized in a mixture of sea-water and alcohol, was placed in a 

 ten per cent solution of common salt until it was evident that its skin 

 was loosened from the body. A cut was then made through the cuticula 

 along a longitudinal line of the body, and the animal placed in tap- 

 water. After the salt had been thoroughly washed out, the worm was 

 cut transversely into pieces short enough for the cuticula to be mounted 

 conveniently on a slide. The cuticula was next peeled off with needles 



