58 SPONGES 
passed through the sareode, where loose pieces may be found, until it is aecu- 
mulated in small parcels when it is encysted. (See Fig. 3, v, v, page 138, 
where I have given two of these encysted parcels of sand: also fig, 9, to the 
right ofa, where I have shown a sand cyst which has either interrupted the 
course of a water tube, or has caused it to become absorbed at its inner termi- 
nation, during the progress of the accumulation of the sand, the latter hypoth- 
sis being the most probable. 
Although the passage of foreign matter through the sarcode of sponges 
to become finally encysted at particular points, may be akin to a similar proc- 
ess in the amoeba and other equally low forms of animal hfe, where the food 
is gathered in ball-like parcels, (See Fig. 4, page 15, where is given a greatly 
enlarged diagram of an amoeba: the unlettered circles being the food balls, ) 
yet in both of these there would appear to be some kind of nervous energy, 
which in the case of the amoeba, is the origin of that impulse which gathers 
the food in balls, and expels that portion which is not absorbed, and in the case 
of the sponge, which passes the intruding sand through the sarcode to become 
finally encysted. The origin of the impulse which causes the amoeba to move, 
srasp-food or propagate by division, and which originates the impulse which 
causes the motion of the cilia in the cells of all species of sponges and which 
causes some species to shrink upon being handled, (See page 43, under Hab- 
its of Horny Sponges) must also be something akin to nervous energy, al- 
though that something is so subtle that it has up to date evaded the investiga- 
tion of the most careful microscopist, even though he be provided with the 
best instrument which skilled labor can give him. 
