820 
DE. J. S. BOWEEBANK ON THE ANATOMY 
structure. Liebeekuhn, in treating of these bodies under the name of motile spores, 
states that he has never succeeded in discerning a “ cell-membrane ” around these par- 
ticles, and my own observations are in perfect accordance with his experiences. The truth 
appears simply to be, that any minute mass of sarcode, whether separated voluntarily or 
involuntarily, has inherent life and locomotive power, and is capable of ultimately deve- 
loping into a perfect sponge ; and in the course of this process the dermal membrane is 
produced at a very early period, and this, surrounding an agglomeration of minute 
masses of sarcode, may have been mistaken by Caetee for a cell-membrane. The same 
author, in his observations “ On the Species, Structure, and Animality of the Freshwater 
Sponges in the Tanks of Bombay,” states, “ that when the transparent spherical capsules 
which contain the granules within the seed-like bodies are liberated by breaking open 
the latter under water in a watch-glass, their first act is to burst ; this takes place after 
the first thirty-six hours ; and their granules, which will presently be seen to be the true 
ova of a proteaniform infusorium, varying in diameter from about the ^ 3^0 pth part of an 
inch to a mere point, gradually and uniformly become spread over the surface of the 
watch-glass. On the second or third day (for this varies) each granule will be observed 
to be provided with an extensible pseudo-pediform base ; and the day after most of the 
largest may be seen slowly progressing by its aid, or gliding over the surface of the 
watch-glass in a globular form by means of some other locomotive organs.” 
This description is strikingly similar to the same author’s account of the masses of 
sarcode separated from the sarcodous lining of the interstitial canals of S])ongilla ; but 
it must be observed that, in the development of the egg, the first act is to liberate itself 
from the membranous envelope ; and the contents thus hatched become movmg masses 
of free sarcode, but without the locomotive cilia that are found on the so-called ova or 
gemmules of the marine sponges, so minutely and accurately described by Dr. Geant 
in his papers “ On the Structure and Functions of the Sponge ” in the ‘ Edinburgh New 
Philosophical Journal,’ vol. ii. p. 129. This author describes the ovum or gemmule of 
Halichondria jpanicea {Hal. incrustans, Johnston), after having floated freely about for a 
period by means of the cilia around its larger extremity, as attaching itself to a fixed 
body by its smaller end and then gradually settling down in the form of a broad flat 
mass, and, after losing its cilia, being gradually developed in the form of the parent 
sponge. Thus every description by these close and accurate observers tends to the con- 
clusion that the multiplication of the sponge is effected by the origination in the ovum, 
or by the agglomeration in the form of gemmules, of particles of sarcode. The action of 
the minute masses of sarcode liberated by the bursting of the envelope of the ovum, and 
their subsequent development, are precisely those of the so-called sponge-cell liberated 
from the mass of the sarcode lining the interstices of the sponge, and of the gemmules 
described by Geant, when sessile : each moves independently at first ; each unites with 
its congeners into one body ; and the results, both in means and end, are precisely the 
same : but their origin is different. The one is a gemmation of sarcode within a proper 
membrane in the form of an egg, while the others are the production of a gemmulg. 
