Anatomy of Stephanoceros Eichhornii. 9 



to meet in the centre, a considerable space exists in this region 

 of the foot. As to whether or not this space is caused by the 

 reagents used I am unable definitely to determine ; anyhow, 

 it is present in all my sections, and is also plainly visible in 

 the same region in Melicerta ringens. Owing to the tapering 

 shape of the foot this space gradually decreases in size as one 

 passes to the attached extremity ; it terminates at the junction 

 of the four pairs of muscles. Anteriorly it continues into 

 the trunk, and thence into the arms, there being, so far as I 

 can discover, no septum dividing them. At first I was in- 

 clined to imagine that the reagent used as a stain had failed 

 to affect the protoplasm of the arms ; but, on farther exami- 

 nation, I found that the arms simply consisted of a delicate 

 cuticle, a continuation from the foot and trunk. Lining this 

 integument is a denser substance, not exhibiting any definite 

 cell-structure. From its greater density I should infer this 

 substance to be a skeletal tissue. 



Zoologists seem fairly agreed that there is a fluid within 

 the body of the animal ; but as to whether or not the " vibratile 

 tags " with their canals are of the nature of a vascular or 

 excretory system opinions seem fairly divided. When com- 

 mencing my study of this Rotifer I hoped to obtain some 

 interesting results with regard to these structures ; but so 

 far 1 have failed to Hud any trace of them in sections. Owing 

 to the hollow nature of the arms one can easily imagine that 

 the animal protrudes from its case by the fluid occupying the 

 body- cavity being forced forward. 



Parasites. — In one of my earliest series of sections of this 

 Rotifer I met with a structure in the region of the posterior 

 third of the body which for a considerable time I was unable 

 to explain. It consists of an ovoid body placed directly under 

 the cuticle and sharply divided from the rest of the Rotiferon 

 by a well-defined membrane. Scattered irregularly within 

 this body are numerous cells, varying considerably in size, and 

 placed excentrically is a large ovoid capsule, bounded by a 

 wall of apparently a chitinous nature, a small opening being 

 visible at the point nearest the cuticle. Lining the interior of 

 this capsule is a thin layer of homogeneous protoplasm, from 

 which extends a delicate fringe of cilia which completely till 

 the cavity (PI. II. fig. 16). Shortly after I met with Dr. 

 Zacharias's paper, and at once recognized my specimen as a 

 species of Trypanococcus, discovered by Prof, von Stein many 

 years ago. In a footnote Dr. Zacharias (loc. cit.) says, " On 

 careful examination of fig. 1 [Stephanoceros Eichhornii) on the 

 first of the four plates which Prof. Leydig has appended to 

 his tine memoir on the structure and systematic position o\i 



