ipoy ] Some Phenomena in Sponges 165 
in so far as the histological character of the syncytial mass is 
fixed for the species. A tiny lump may metamorphose into 
a sponge, or may first fuse with many such lumps, the aggre- 
gate also producing but a single sponge although a larger 
one. In a word we are not dealing with embryonic bodies of 
complicated organization but with a reproductive or regener- 
ative tissue which we may start on its upward path of differ- 
entiation in almost any desired quantity. A striking illus- 
tration of this nature of the material is afforded by the fol- 
lowing experiment. The tissue in the shape of tiny lumps 
was poured out in such wise that it formed continuous sheets 
about one millimeter thick. Such sheets were then cut into 
pieces, each about one cubic millimeter. These were hung 
in bolting cloth bags in an outside live-box. Some of the 
pieces in spite of such rough handling metamorphosed into 
functional sponges. 
Even where the embryonic bodies of sponges have a fixed 
structure and size, as in the case of the ciliated larva, the 
potential nature as displayed in later development, is not 
fixed in the matter of individuality. Such a body may form 
a single individual or may fuse with some of its fellows to 
form a larger individual differing from the one-larva sponge 
only in size. It is then in spite of its definiteness of shape 
and size, essentially like a lump of regenerative tissue in that 
whether it develops into a whole sponge or a part of a sponge 
depends not on its own structure but on whether it is given 
a good opportunity of fusing with a similar mass. A paral- 
lel case to the coalescence of larvae is afforded by the gem- 
mules of fresh water sponges. Mr. M. E. Henriksen in a 
manuscript account submitted to me a year ago, describes the 
fusion of gemmules to form a single sponge. 
S in the preceding description I have passed over the question 
as to the precise nature of the cells which combine to form 
the masses of regenerative tissue. On this point as on the 
histological details in general I hope to have more to say 
later. Nevertheless the phenomena are so simple that obser- 
vation of the living tissue reveals much, probably indeed all 
