114 The American SpongiUa. 



way ouly a turbulence of floating matter is sustained, but the gene- 

 ral, great current is clue 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 sepa- 

 rated, and the circulatory apartment is very deep ; and between 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 gene- 

 ral apartment, it is plain now (although our actual observation on 

 this point is very defective), may contract or expand without dis- 

 turbing 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 efi'erent ostiole closed, and expanding, draw in current 

 through its open afferent ostioles. 



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

 pleting 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 present residence. Unfor- 

 tunately 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 circumstances from carrying out our 

 designs. 



In regard to the afferent and efferent canals, seen by Carter* 

 in the monadigerous mass {" ixirencJujma " Carter), we have not met 

 with any trace of them in the species described in this article. It 

 is possible that they may exist in the oldest and largest individuals, 

 but as we worked only on very small and transparent specimens, 

 our direct observations, in this respect, strictly apply to the latter. 

 It is more likely that ours is a different genus from the Spongilla 

 of Carter, in favour of which we cite the curious fact that each 

 aperture, in the inner division (not mentioned by Carter) of the 

 investing membrane, exactly overlies and is inseparable from the 

 entrance to a monad chamber (" amjniUaceous sac " ; 2Jcirtim, Carter) ; 

 so that whatever enters these chambers must go out by the same 

 way that it came in ; not out into a system of branching canals, 

 burrowed in the monadigerous mass, but into the great circulatory 

 apartment. — SiUimans American Journal, Dec, 1870. 

 * 'Ann. Mag. Nat. Hist.,' 1857, vt S'ip. 



