AND PHYSIOLOGY OP THE SPONGIAD^. 
761 
the interstitial membrane of the honeycomb sponge of commerce, with the sarcode in its 
natural condition, filled with the remains of the nutrient molecules in a collapsed state. 
Figs. 13 & 14, Plate XXVIII., exhibit the same tissues with the addition of nucleated 
cells immersed in the sarcode. In the sponges of commerce it is exceedingly largely 
developed, and nothing can be more different in character than their soft and flexible 
skeletons and the animal in its natural condition. Specimens of it in this state, which 
have been preserved in spirit immediately on being taken from the sea, have the whole 
of their interior nearly as solid and firm as a piece of animal liver, the colour being a very 
light grey or nearly white. While the sponge, as a whole, is sensitive and amenable 
to disturbing causes, the sarcode does not appear to be especially so, as I have frequently 
observed a minute parasitic annelid which infests the interior of 8pongilla fluviatilis, 
passing rapidly over the sarcodous sm’faces, and biting pieces out of its substance with- 
out apparently creating the slightest sensation to the sarcode, or at all interfering with 
the general action of the internal organs of the sponge ; and in many cases we find fora- 
miniferous and other minute creatures permanently located in its large cavities without 
appearing to cause it the slightest inconvenience. 
When separated from the living sponge, it has at certain periods an inherent power of 
locomotion ; small detached masses of it may be observed slowly but continuously 
changing their form, and occasionally progressing in different directions ; and Cartee, in 
his valuable ‘ History of the Freshwater Sponges of Bombay,’ describes such detached 
masses of sarcode, when progressing and encountering a fixed point, as dividing longi- 
tudinally to avoid the impediment, and again uniting when it has been passed. This 
gliding motion appears to be dependent on an inherent contractile power, as no cilia 
have been detected on the surface of such locomotive masses. DujARDm has recorded 
similar movements in portions of the sarcodous substance from specimens of his genus 
Halisarca ; and similar observations have been recorded by Liebeekuhn and other 
writers during their observations of the Spongiadse. I have frequently, at different 
seasons of the year, taken portions of the sarcode from living and healthy specimens of 
Spongilla, in which I could not by the closest observation detect these motions, which 
are so readily to be seen at other periods of their existence ; and even at the same period 
of the year the sarcode of some specimens exhibits these motions, while in others they 
could not be detected. I have often sought for these phenomena in portions of the 
sarcode of Halichondria jpanicea^ Hymeniacidon caruncula, and other marine species, but 
I have never yet been fortunate enough to detect them. It is highly probable that the 
capability of such motions exists in the sarcode of these and other marine species for a 
limited period, but it does not appear that such powers of motion are a constant con- 
dition of this substance. 
