Coalescence and Regeneration in Sponges 253 



cover glasses, was made. The preparations were examined at 

 short intervals with the microscope. The cells of these three 

 species are colored very differently, and are therefore easily dis- 

 tinguished, at least as soon as fusion sets in and little masses of 

 cells begin to be formed. In all the experiments the cells and 

 cell-masses of a species combined, and not the cells ot different 

 species. Thus in the admixture of Microciona and Lissoden- 

 doryx, Microciona regenerative masses and Lissodendoryx regen- 

 erative masses were produced. Similarly when Microciona and 

 Stylotella cells were mixed, the resultant masses were pure, some 

 Microciona, some Stylotella. The Microciona masses in these 

 experiments were hardy. They continued to develop and in 

 some preparations metamorphosed. The cell masses of the other 

 two species while they reached a considerable size were not hardy, 

 most dying soon although some began the process of metamor- 

 phosis. 



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 physio- 

 logical state of the protoplasm, so the regenerative cells and cell 

 masses of different species may be made to combine under abnor- 

 mal conditions. The more promising task is however to find 

 allied species and subspecies, the regenerative tissue of which 

 will combine under natural conditions. Such forms, I take it, 

 should be sought among the horny sponges and the monactinellids 

 with abundant 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* says that he has often observed two or 



* Embryogenie des Eponges. Arch, de Zool. Exp. et Gen., p. 400, 1892. 



