24 BULLETIN OF THE BUREAU OF FISHERIES. 



tendency to contract becomes active and the irregular little sheet gradually draws and 

 rolls up to form a ball. 



The tissue in general (reticula and sheets) was on August 27 broken up with pipette 

 into portions from a few to 20 mm. wide and 0..5 to i mm. thick. All these continue 

 to contract and curl up. On August 30 these masses were more compact and still quite 

 free from the substratum. Although kept for several days they remained unchanged 

 and did not attach. 



Experiment record 12, August 28, 1907. — Question involved: Does a mixture of very 

 fine pressed-out tissue and fairly coarse tissue offer any advantage, for the growth of 

 sponges, over coarse tissue alone ? In general it does. The fine particles as they meta- 

 morphose tend to fasten down the larger masses. 



Pressed out Microcioiia tissue was prepared in abundance. In the course of 30 

 minutes it was freed with pipette from bottom of dish and collected in center. It was 

 then strewn over slides. Fusion had gone on rapidly and the bulk of the tissue was 

 already in the shape of rather coarse lumps. On some slides only this coarse tissue 

 was strewn. On a second set of slides, after the coarse tissue had been strewn, a quantity 

 of very fine particles was deposited on and between the coarser masses. On all slides 

 the tissue during the next two to three hours attached and underwent the preliminary 

 steps toward plasmodium formation. During the next few hours there was a marked 

 difference between the two sets of slides. Where coarse tissue alone had been strewn 

 local contraction brought into existence masses (spheroidal, irregular, reticulated, etc.) 

 of considerable size and thickness and without much interconnection. Where coarse and 

 fine tissue had been strewn there was formed a continuous network of small, thin, 

 flat Plasmodia exhibiting local enlargements and thickenings which represented the 

 coarse masses produced by the early fusion of the tissue. The indication was that the 

 second set of slides would metamorphose first. Nevertheless both sets went ahead in 

 the metamorphosis at about the same rate. 



In this instance the coarser and comparatively massive collections of tissue con- 

 tinued to retain their attachment to the substratum. This is not always the case. 

 In handling large numbers of such preparations during the following summer my assist- 

 ant, Mr. Bridgers, found that the practice of strewing very fine particles of tissue over 

 the preparation that had just been made was often useful. It sometimes happens 

 that the reticula or perforated plates formed by the tissue that has been strewn over 

 the slide or shell begins to separate from the substratum, curling up at the edges. If 

 very fine tissue has been strewn over the slide, it forms sm.all, flat, and thin plasmodia, 

 which fasten down the larger ones. As already said, if one wishes to get sponges, it is 

 important that the plasmodial masses make firm attachment to the substratum before 

 the preparation is put in the live box. 



Experiment record 13, July 2, igo8. — Question involved: What difference in behavior 

 is there between tissue pressed out of a fresh sponge and tissue pressed from a sponge 

 kept several days in the aquarium ? Tissue obtained from the sponge kept in aquarium 

 is slow to metamorjjhose, but can do so in the open water. 



