80 Prof. H. James-Clark on the American Spongilla 



ostioles. Nowhere else are vibrating or non-vibrating cilia or 

 cilia-like bodies to be met with than in the monad-chambers ; 

 and since the efferent ostioles are irregularly interspersed 

 among the much more numerous aflferent ostioles, we cannot 

 conceive how the flagella in any way could influence currents 

 to move in a particular direction from the smaller apertures 

 toward the larger ones. They no doubt keep u]3 a direct flow 

 of matter into the sunken chambers ; but the current comes 

 from the inner depths of the circulatory apartment, and far 

 away from the ostioles. In this way, only a turbulence of float- 

 ing matter is sustained • but the general great current is due to 

 a far different cause. We conceive that the contraction and 

 expansion of the body-mass in general, modified by the alternate 

 opening and closing of the afferent and efferent ostioles, is the 

 true motive power in this phenomenon. We have observed, 

 often, that the outer division of the investing membrane is not 

 kept at a uniform distance from the central monadigerous mass : 

 at one place it will be found to be close to its inner division, so 

 that the circulatory apartment is very shallow there ; while at 

 another point the two divisions of the membrane are widely 

 separated, and the circulatory apartment is very deep, and be- 

 tween the shallow and the deep apartments a curtain is drawn, 

 more or less completely, extending from one pillar-like bundle 

 of spicules to another. Each of these temporarily enclosed 

 portions of the general apartment, it is plain now (although 

 our actual observation on this point is very defective) , may 

 contract or expand without disturbing the contents of any 

 other. Such an apartment, with its afferent ostioles closed, 

 may be contracting and forcing a current out at its efferent 

 ostiole, while a neighbouring apartment may have its efferent 

 ostiole closed, and, expanding, draw in currents through its 

 open afferent ostioles. 



We regret that we have not the means, in this locality, for 

 completing these researches. Our specimens were gathered 

 and studied on the spot where they lived, in the western part 

 of Massachusetts, several hundred miles away from our pre- 

 sent residence. Unfortunately we put off" the attempt to feed 

 the sponge with coloured matter until we had completed other 

 methods of investigation, and then we were prevented by cir- 

 cumstances from carrying out our designs. 



In regard to the afferent and efferent canals seen by Carter 

 (Ann. & Mag. Nat. Hist. 1857, ut suj:).) in the monadigerous mass 

 {^^ parenchyma,'''' Carter), we have not met with any trace of 

 them in the species described in this article. It is possible 

 they may exist in the oldest and largest individuals ; but as we 

 worked only on very small and transparent specimens, our 



