DEVELOPMENT OF SPONGES FROM DISSOCIATED TISSUE CELLS. 1 5 



Fusion of the small masses continued. In general red mass fused with red mass, and 

 green mass with green mass. Nevertheless fusion was also observed in some instances 

 between red and green masses, the two putting out pseudopodia on the confronting 

 surfaces, and the masses later coalescing bodily. Such fusions, as the further history of 

 the watch glass showed, must have been temporary or the combined masses soon died. 

 For as fusion progressed and the masses increased in size, the distinction between red 

 and green tissue became more evident. In the course of one to two days the red tissue 

 went through the preliminary step of metamorphosis, flattening out in shape of small thin 

 Plasmodia, which established connection with one another. The green (Lissodendoryx) 

 tissue remained in compact masses. In figure 32 the two kinds of masses are shown at 

 this stage of development. The Lissodendoryx tissue is stippled, the Microciona is 

 unstippled. It will be seen that, while the Microciona and Lissodendoryx masses are 

 sometimes closely applied, they are distinct bodies. 



The Microciona masses increased in size, and on August 16 had completed the 

 metamorphosis, viz, had flagellated chambers and some canals. The Lissodendoryx 

 masses gradually diminished in number, doubtless dying. Those that survived until 

 August 16 were of about sizes shown in figure 32, but had flattened out somewhat. 



In this experiment fusion took place between the cells and cell masses of the same 

 species. Whatever fusion there was between the two kinds of tissue was insignificant 

 in amount. 



Experiment record. — In preparing for the last experiment, as stated above, the 

 coarser masses were removed from the watch glasses containing respectivelv the two 

 kinds of tissue. A quantity of these coarser masses of Microciona tissue was now (Aug. 9, 

 1907) thoroughly mixed with a like quantity of similar Lissodendoryx tissue in a watch 

 glass. Fusion went on, and, as before, between masses of the same species. The red 

 (Microciona) masses increased greatly in size, and on August 1 2 had the shape of irregular 

 Plasmodia, which were flattened and thoroughly adherent to the glass, the different 

 Plasmodia more or less interconnected. In figure 29 some of the interconnected 

 Plasmodia are represented (unstippled) at this stage. The green (Lissodendoryx) 

 masses resulting from continued fusion did not become so large. Many of them 

 disappeared (died or failed to attach well and were washed off?) during August 9 

 to 12. Those that remained on August 12 were compact and not flattened. In this 

 condition they appear (stippled masses) in figure 29. It will be seen that in some cases 

 they lie in close contact with the Microciona plasmodia, and may even be surrounded by 

 the latter, but no real union between the two kinds of bodies exists. By August 1 6 the 

 Microciona plasmodia had metamorphosed completely, viz, were thin incrustations with 

 flagellated chambers and canals. A good many of the Lissodendoryx masses were still left 

 on this date, some in shape of fairly thick compact masses, others flattened out and thin. 

 None had metamorphosed. Possibly if the mixture were made in dishes at once exposed 

 to the water of the harbor, better results might be had. 



Experiment record, August 9, ipoj. — Dissociated cells of Microciona and Lisso- 

 dendoryx were prepared in the usual way and the two tissues thoroughly mixed in equal 



