igoy \ Some Phenomena in Sponges 167 
the granular cells go to make up the balls. The play of pseu- 
dopodia at the periphery of such balls, which results in the 
incorporation of free cells and in the fusion of balls to form 
larger masses, is easily watched. Along with such a cover 
glass preparation it is convenient to have some of the 
squeezed-out tissue in a watch glass of sea-water. In the 
watch glass preparation it is instructive to watch with a two- 
thirds or one-half objective the fusion of the cell conglomer- 
ates to form masses like those strewn on covers, slides, etc. 
These observations on the early steps in the formation of 
the masses of regenerative tissue make it plain that such 
masses are composed chiefly of the spheroidal, granular cells 
(amoebocytes or archaeocytes), but that nevertheless other 
cells, collar cells and more or less hyaline cells also 
enter into their composition. I may recall the fact that in 
the formation of regenerative masses in a degenerating 
sponge , 3 the evidence from sections, which is the only evi- 
dence available in the case, points to the conclusion that the 
collar cells help to form the syncytial tissue of the masses. 
The question of interest lying at the heart of this matter may 
be so formulated: can particles of the Microciona protoplasm 
differentiate into functional collar cells and, when the occa- 
sion arises, change back into unspecialized masses capable of 
combining with other masses of unspecialized protoplasm to 
form a regenerative body? The facts to which I have just 
alluded support this idea, and indicate that the immediate 
problem is one worth pursuing farther as a good case of tem- 
porary differentiation of protoplasm in the metazoa analo- 
gous to the temporary specialization of the cell individual 
which occurs in such colonial protazoa as Protospongia . 4 
As far as the amoebocytes are concerned it is certain that 
they have great regenerative power. Weltner in a recent 
$ 
3 A new method by which sponges may be artificially reared, Science, n. 
s., vol. xxv, no. 649, 1907. 
4 Metschnikoff, Embry ologische Studien an Medusen, p. 147, 1886. 
