38 Mr. F. S. Conant on the Cubomedusas. 



lamellae pointed strongly toward a relationship with such 

 Hydromedusge as, for example, Liriope (Trachomedus*) , 

 another part, around the margin of the bell, gave evidence 

 equally as good to the effect that the velarium was formed 

 by the fusion of marginal lobes and that the view which con- 

 siders it not homologous with the Hydroraedusan velum is 

 therefore correct. The question as to the affinities of the 

 Cubomedusffi must wait until the development is known. 



The nervous system has been described by Glaus *, and 

 more recently in greater detail by Schewiakoff t' With the 

 latter's conclusions as to the structure of retina and vitreous 

 body of the complex eyes on the sensory clubs I am unable 

 to agree. Schewiakoff's conception of the structure is in 

 brief as follows : — 



a. The retina is made up of two types of cells, pigment 

 and visual, which are figured as alternating regularly. The 

 pigment-cells are cone-shaped ; the visual are spindle-shaped, 

 with their nuclei lying in the swollen central portion of the 

 spindle at a lower level than the nuclei of the supporting 

 pigment-cells. 



h. From the visual cells extend rod-like processes into the 

 vitreous body (which lies between the retina and lens), lying 

 in canals in the vitreous body. 



c. In the vitreous body separate cone-shaped streaks of 

 pigment overlie the pigment-cells, which do not, however, 

 form part of those cells. 



d. Apart from these pigment-streaks and the rod-like 

 processes of the visual cells_, the vitreous body is structureless, 

 probably a secretion of the pigment-cells. 



The conclusions reached upon the same points by the study 

 of the two Jamaica species are : — 



a. There is not good evidence of two distinct types of cells 

 in the retina — cone-shaped pigment-cells and spindle-shaped 

 visual cells, with the nuclei of the latter at a lower level than 

 those of the former. 



b. The rod-like processes in the vitreous body exist, though 

 not referable to a special type of cell in the retina. 



c. The cone-shaped streaks of pigment in the vitreous 

 body belong to the underlying pigment-cells, in fact are 

 direct continuations of them, and at their distal ends they are 

 prolonged into fibrous processes lying in canals of the vitreous 

 body exactly like the visual rod-like processes of Schewiakoff. 



* '' Ueber Charyhdea marsupialis," Arb. aus d. zool. Inst. d. Univ. 

 Wien, Bd. ii. Heft 2 (1878). 



t " Beitrage zur Kentniss des Acalephenauges," Morph. Jabrb. Bd. xv. 

 Heft 1 (1889). 



