210 Prof. H. James-Clark on the Spongige ciliatse 



with which the free end of each one is endowed. The whole 

 bristling mass revolves alternately from right to left and from 

 left to right, whirling upon its slender pivot with such a degree 

 of freedom that one might almost suspect that it merely rested 

 uj)on it, and had no truer adliesion to it than the juggler's top 

 to the end of the hdton upon which it spins. The largest 

 of these twirling groups contains as many as fifty fusiform 

 bodies; but most frequently not more than half that number 

 are grouped together ; and from this they vary in decreasing 

 numbers down to only one or tv\^o (fig. 48) upon each filamen- 

 tous twig. In the last instances the bodies are comparatively 

 quiet, scarcely moving out of focus at each spasmodic twitch 

 of the arcuate filament. On this account, and because they 

 offer an miobstructed view, the latter are by far the most 

 available as objects for the investigation of their internal 

 organization. 



" The relationship of the individual monads to the whole 

 colony must, however, be studied where they are more nume- 

 rously congregated, since, as will be shown presently, each 

 monad sustains a definite relation to every other one and to the 

 twig to which it is attached." 



" Fo7'm &c. — The adult monads (figs. 47, 48, ind) have a 

 truncate fusiform shape, and are slightly but quite appreciably 

 flattened on two opposite sides, so that, in an end view, they 

 appear to be broadly oval transversely. The attached end 

 tapers gradually to a point ; and on this account it is difficult 

 to determine where the body ends and the twig begins. All of 

 the members of a grouj) radiate from a common point of at- 

 tachment, to which they adliere by their tapering filamentous 

 ends (fig. 48, ^J6?^). The free end is trmicate ; but one corner 

 of it (as if in continuation of the line along which the opposite 

 flattened sides meet) projects in the form of a rather blunt tri- 

 angular beak {Ip). At the inner edge of the base of this beak 

 lies the mouth (w), to which the former, as frequent observa- 

 tion has proved, acts as a lip or prehensile organ when food is 

 taken into the body. The prevailing tint is a more or less 

 uniform light gamboge, without the least trace of an eye-spot 

 of any colour. 



" A most singular uniformity prevails in the arrangement 

 of the several members of a group. Each monad [md) is at- 

 tached to its mooring in such a position that its flattened sides 

 lie parallelwise with those of its nearest neighbour ; and the 

 beak {Ip) projects from that corner of the head which is most 

 distant from the twig {pd). To give a full idea of the pecu- 

 liarity of this arrangement, it must be stated here that the 

 rigid, arcuate, spasmodically twitching filament {ji) mentioned 



