DEVELOPMENT OF SPONGES FROM DISSOCIATED TISSUE CELLS. 1 9 



Many of the latter, often ranging from 400/4 down, cohere and make up loose masses of 

 any shape which may be several millimeters in diameter. 



Fragments of the entire aggregation about i mm. in diameter were now hung in a 

 small bolting-cloth bag which was suspended in a live box floating in the harbor. The 

 bag used was rectangular and flat, 60 mm. by 20 mm. on the side and about 2 mm. deep. 

 The two sides of the bag were held apart by wooden strips, and the bag was divided 

 into two compartments. In each compartment several fragments were placed. The 

 bag was opened July 23, and it was found that the masses had not grown or attached. 

 Some had died. The rest were spheroidal and embedded in a mass of debris. 



The result of the experiment docs not really indicate that the tissue masses were 

 nonregenerative. A later experiment shows that similar masses obtained from a fresh 

 sponge can actually regenerate. Possibly the masses of regenerative tissue obtained 

 from the degenerated sponge require more careful handling. 



Experiment record 4, July 79, 1907. — Results: (i) When the tissue is teased out 

 of a fresh sponge in which no degeneration-regeneration phenomena have occurred, 

 the cells and cell masses combine; (2) the compact masses of tissue so obtained trans- 

 form into sponges when removed to the harbor. 



A branched specimen of Microciona kept only one day in aquarium, and as yet 

 showing no signs of degeneration, was used. Sponge was cut in pieces and pieces teased 

 with needles in watch glass of filtered sea water. Cells and minute cell masses were 

 liberated in great quantity. These began to fuse, displaying amoeboid activities. 

 About one hour later the fusion is aided by gently forcing the tissue to center of watch 

 glass with pipette. The bulk of the tissue is thus gathered at the center, where it forms 

 a loose heap about 7 mm. in diameter. One hour later the general aggregation in the 

 center consists of rounded and irregular masses and lobes. The watch glass is now im- 

 mersed in crystallization dish of sea water. Three such watch glasses were prepared. 

 In one a good many small skeletal fragments of the teased sponge were left in the aggre- 

 gation of tissue. In the other glasses an effort was made to remove all skeletal fragments. 



The aggregated heaps of sponge tissue, each consisting of many loosely adhering 

 rounded or irregular masses of compact tissue, were divided up some hours later into 

 seven lots. Each lot was put into a compartment of a bolting cloth bag, and the bags 

 suspended in live box. On July 23 the bags were opened and the sponge tissue in each 

 compartment was found to consist of distinct and separate masses, many of which 

 gave signs of development. Some of these masses were now kept in crystallization 

 dishes of sea water containing Ulva, others were returned to the bags. On July 29 a 

 final examination showed that many of the masses in the bags had completely metamor- 

 phosed, viz, had oscula, flagellated chambers, and canals. Other masses had no con- 

 spicuous oscula or canals, but had partially metamorphosed. None of the masses kept 

 in laboratory dishes had completely metamorphosed. 



In metamorphosing some of the masses had flattened out greatly, spreading as 

 incrustations over the bolting cloth, the meshes in which were thus completely covered 

 over. Others had remained as compact masses. One such is shown in figure 26. In 



