21G CTENOPIIOR.^. Part II. 



The adaptation of means to an end is nowhere in the animal kingdom more 

 beautifnlly and phiinly disphij'ed than in the mode of disposition of the simple 

 material whieh constitutes, at the same time, the mass and the moving power of 

 this animal : a specialization by arrangement, without a segregation, as a distinct 

 system apart from the other organs. If the greater part of the Ijody of certain 

 Mollusca is subservient to muscular action, how much more extensively does this 

 obtain in the Ctenophora\ 



Viewing the body of Plenrobrachia from the actinal pole {Fi(j. 21 (i\ the -whole 

 mass appears, at first sight, to be composed of an aggregation of cells {m vr), 

 which radiate in every direction from the centre to the periphery, as if an ex- 

 emplification of the radiate type to which this animal Ijclongs. It is true, these 

 cells are arranged as we have here described ; they do not, however, occu2)y the 

 whole of the space through which they project, but are intimately interw^oven -with 

 the cells of another system {p p"), diverging from the tentacular sockets {j) to 

 the periphery. The radiating system, however, is the most extensive, and pervades 

 almost every region of the body : in fixct, the only portions which it does not 

 occupy are a small spiice lying in a direct course Ijetween the tentacular sockets 

 and the periphery, and also a thin layer of the peripherj-, which is exclusively 

 devoted to the system of cells {n 11}) which traverse the spaces between and under 

 the locomotive flappei's. In all these systems the longer axes of the component 

 cells trend in the lines of radiation of each system to Avhich the}' belong : in fact, 

 it is their longitudinal outline which gives the characteristic fibre-like appearance to 

 the mass of the Ijody. Tins will suffice to give an idea of the general disposition 

 of these cells, and of tlieir relation to each other ; but each system needs a much 

 fuller treatment by itself, in order to elucidate its share of influence upon the 

 movements of the Ijody. 



For the sake of convenience, we will describe the peripheric system first. It 

 will be seen by the figures drawn ft-om the actinal and abactinal poles {Figs. 20 and 

 21), that the outline of the body is waved or slightly lol)e(l, the lobes corresponding 

 to the spaces between the rows of locomotive flappers (/' /-), so that there may be 

 said to be eight broad ribs alternating with as many narrow and shallow furrows, 

 extending like meridians from the actinal to the aljactinal areas. The proportionate 

 breadth of the ribs may be ascertained by inspecting the figures, and they are 

 described more fully in another place. Now, the j^eripheric cellulo-motory system 

 is divided into two sets of layers, the one corresponding to the broad ribs and 

 the other to the shallow furrows. The first system (« n^) is by fiir the most 

 extensive, both in breadth and depth. The surface of each broad rib is at the 

 same time the outer convex surface {Fig. 21 11) of a broad band of transversely 

 trending cells ; and the inner face {n^) of each Ijand has the same degree of cur- 



