21 Ocel. 
CCELENTEEATA. 
furthered by the flapping of the body-lobes ; in Cesium, it is chiefly, if 
not entirely, due to the strong muscles developed superficially in a direc- 
tion parallel to that of the longitudinal diameter of the body. The 
central portion of the nervous system is the sense-body at the ab-oral 
pole ; its radial portions eight bands of modified ectodermal cells, which 
are continued into the ciliated furrows and the cells supporting the 
combs (coalesced cilia) of the ribs ; the nervous elements themselves 
forming, in this manner, the chief locomotory organs [I]. The auditory 
organ, a group of lithocysts, constantly growing through addition of new 
material, is suspended on four springs, continuations of the ciliary rows ; 
it regulates the locomotory play of the combs. With the auditory organ, 
two or four eye-specks are probably at least sometimes associated, as in 
acraspedote Medusae. On the other hand, the nervous elements of Eimer 
are utterly rejected as such ; they belong to the connective tissue or are 
immigrated, ramified, muscular cells, to which the soft, jelly-like body 
owes its contractility and elasticity. The ordinary character of the 
muscles in Ctenophora is therefore very different from that of the true 
Medusae, when a stronger muscular force is not needed, as in Cesium. 
This genus is also endowed with a peculiar play of colours, taking, when 
irritated, an intense blue colour, which resides in peculiar cells of the 
ectoderm, that in the state of repose are yellowish ; this faculty of 
changing colour is diminished by repeated irritation in the same manner 
as the faculty of phosphorescence. The observation is also important, that 
the Cienophora 2 j:q — with a single doubtful exception — not cnidophorous ; 
the so-termed “ lasso cells” are organs sui generis, “prehensile cells,” (2) 
not cnidae. 
Buekers has studied the integument, the gastro-vascular apparatus, 
and the general histology of Cesium (1). He also rejects Elmer’s inter- 
pretation of the fibrillar and cellular elements of the jelly, which are 
regarded only as elements of connective tissue, and distinguished rather 
sharply from the muscular. The fibrillar and ganglionic elements 
observed below the ribs and below the dorsal groups of sense-cells — 
apparently not observed by Chun — are perhaps (rather than a part of those 
described as such by the last-named observer) the true nervous elements. 
The ab-oral orifices of the funnel vessels serve, according to the hypo- 
thesis of the author, to furnish the water necessary for the erection of the 
tentacles, and — by admitting water or giving exit to a part of the gastro- 
vascular fluid — to enable the animal to rise or sink in the water, but in 
a reverse manner to Elmer’s interpretation. Buekers also was unable 
to detect urticating cells. 
