56 JOHNS HOPKINS UNIVERSITY MORPHOLOGICAL MONOGRAPHS. 



other respects too little. This is not to be wondered at, since his mate- 

 rial, to judge from a single statement, consisted of but twelve marginal 

 bodies, and, moreover, the work on Charybdea forms but one portion 

 of a paper that is excellent for the clearness of its descriptions and illus- 

 trations. 



Before leaving the subject I must mention that Wilson suggested 

 from his observations on Chiropsalmus that the vitreous body had a 

 prismatic structure, but he was probably mistaken when he thought he 

 found evidence of nuclei in it. Claus says that the retina is composed of 

 pigment and rod cells alternating, and Wilson agrees with him, but 

 under a sketch of a sense cell from the nerve he makes the express state- 

 ment "not very well preserved." It seems very probable, therefore, that 

 he followed Claus's interpretation rather than independent observations, 

 and Claus interpreted his results very much by analogy of what had been 

 found in other forms. 



The smaller complex eye which is represented in Fig. 69 agrees in 

 structure very closely with the larger. The chief differences are that 

 sections do not show pigment extending into the vitreous body, that 

 there is no " capsule " to the lens, and that the lens seems to be supported 

 by a kind of stalk formed by a thickening of gelatine of the supporting 

 lamella (si}. The gelatinous thickening lies between the lens and an out- 

 growth of endodermal cells (en) from the canal of the club. This 

 outgrowth is a constant feature, figured by Claus and Schewiakoff for 

 Charybdea, and by Wilson for Chiropsalmus, and found in Tripedalia 

 also. The regularity of its appearance in all three genera leads one to 

 suspect that it may have some significance not yet understood. 



Just above the smaller eye there lies a mass of cells of peculiar 

 structure (Fig. 69, nc). They are of a rounded polygonal contour, with a 

 comparatively small circular nucleus in the centre, and are found in 

 this region only. In and amongst them bundles of fibrous tissue are 

 found in the sections, which pass from the surface cells to the supporting 

 lamella. Claus describes the contents of these cells as coarsely granular 

 protoplasm and says they cannot be taken for ganglion cells. He is 

 inclined to believe that they play the part of a special supporting tissue. 

 Schewiakoff, on the other hand, is convinced that they are ganglion cells, 

 and finds processes passing out from them ('89, Taf. II, Fig. 22). I find, 

 however, that the cell contours are perfectly regular and clearly without 

 processes, and it is incomprehensible to me how, if his material was at all 

 well preserved, he could for a moment have taken them for the same 



