170 Journal of the Mitchell Society [ December 
not hardy, most dying soon although some began the process 
of metamorphosis. 
These three species are so unlike that there was little 
ground in the beginning for the expectation that coalescence 
would take place. Possibly as in the cases where fusion of 
egg and sperm of different species is induced through some 
alteration in the physiological state of protoplasm, so the 
generative cells and cell masses of different species may be 
made to combine under abnormal conditions. The more 
promising task is however to find allied species and subspe- 
cies, the regenerative tissue of which will combine under nat- 
ural conditions. Such forms, I take it, should be sought 
among the horny sponges and the monactinellids with abun- 
dant horny matter. 
Ill 
The tendency to fuse so vigorously displayed by the cells 
and cell masses of regenerative tissue led me to examine into 
the power that larvae have to fuse with one another and the 
capacity for development in the resultant mass. Delage and 
others have remarked on the not infrequent occurrence 
of fusion between sponge larvae. Delage 8 says that he has 
often observed two or several larvae unite to form a single 
sponge “which has from the start several cloacas.” 
I find that this power to fuse displayed by the larvae is one 
that is easy to control. Fusion between the larvae will read- 
ily take place if they are brought in contact at the critical 
time when the ciliated epithelium is being replaced by the 
permanent flat epithelium. At this time they will fuse in 
twos or threes or in larger number up to and over one hun- 
dred. The smaller composite masses composed of as many 
as five or six larvae metamorphose into sponges. The larger 
masses composed of many larvae did not metamorphose in my 
experiments but experience with the regenerative tissue sug- 
gests that such masses would metamorphose if certain 
mechanical difficulties due to the great size of the mass were ? 
8 Embry ong^nie des Eponges. Arch, de Zool. Exp. et G£n. , p. 400, 1892. 
