DEVELOPMENT OF SPONGES FROM DISSOCIATED TISSUE CELLS. 1 7 



edge. Three small irregular flattened Stylotella masses were selected, and were placed 

 upon the Microciona. 



The condition of these plasmodia on the next day at 3 p. m. is shown in figure 30. 

 The Microciona reticulum has contracted into a compact ovoidal body. The Stylotella 

 masses have fused with one another and form the upper irregular mass lying upon the 

 Microciona. The two tissue masses are tightly adherent, but there is no fusion. Other 

 similar attempts to bring about fusion between plasmodial masses of the two species 

 were made with the same negative result. 



EARLIER EXPERIMENTS ON MICROCIONA CHRONOLOGICALLY ARRANGED. 



For the use of those who may carry on investigations such as are reported in this 

 paper I here append some of the earlier experiments leading up to the method finally 

 practiced. The general account given for Microciona is based on a large number of 

 experiments made in the latter part of the summer of 1907 and during the summer of 

 1908. About 200 specimens of Microciona were grown by this method during the two 

 summers. The work of 1908 was under the direct charge of my assistant, Mr. R. R. 

 Bridgets. 



Experiment record j, August 2, igo6. — Question involved: If regenerating tissue 

 that is formed in a degenerating sponge is forcibly freed from the sponge and broken 

 up, will the elements recombine outside the sponge body ? They do. 



A branched specimen of Microciona that had been kept in an aquarium long enough 

 for degeneration to have begun was used. In this state the sponge tissue had died in 

 or retreated from the superficial parts of the lobes, which however contained a core of 

 bright red and dense live tissue. The same tissue forms here and there irregular masses 

 on the surface. I have shown experimentally that in Stylotella masses of similar tissue 

 have the power of developing into perfect sponges. The tissue therefore is regenerative 

 tissue. 



Lobes of the sponge were teased in a watch glass of filtered sea water with needles 

 in such a way as to liberate and break up the regenerative tissue into cells and small 

 cell agglomerates. Many of the cells are more or less spheroidal and contain granules 

 and spheroidal inclusions of varying size. Many inclusions are reddish and the cell 

 may in consequence appear of an opaque red color. Such cells while under observation 

 throw out hyaline colorless pseudopodia, some rounded, some fine and elongated. An 

 infinite number of smaller cells, some with granular or spheroidal inclusions, some 

 nearly or quite hyaline, are also to be seen. 



The cell agglomerates are opaque. They are probably made up of both spheroidal 

 and smaller cells. They certainly include numbers of the spheroidal type. Round the 

 periphery pseudopodial activity was watched. The pseudopodia were for the most 

 part rounded, but some were elongated and pointed. Whatever locomotory motion the 

 mass makes is slow and feeble. 



By gently shaking the watch glass the cell agglomerates were brought together, 

 and repeated instances of fusion between the masses were observed. 



