NOTES ON PLYMOUTH SPONGES. 377 



often with little even of seaweed hardy enougli to bear company — 

 exposed for hours every day to sun, rain, or wind. 



I made some tentative experiments as to the endurance of ^S*. com- 

 prcssum, a brief summary of which, with figures of the metamorphosed 

 collar-cells, appeared in " The Collar-cells of Heterocoela," Q. J. M. S., 

 vol. 38. Though they would have been better if comparative 

 with studies on other species, the results by themselves are fairly 

 striking. 



(1) Several sponges were gathered at 1 p.m. on February 6th at low 

 neap tide. They were taken from positions on the tops of rocks, free 

 from all water or seaweed, and placed, without more water than they 

 contained, in a small empty corked bottle. On February 7th, at 1 p.m., 

 a section from a large specimen was examined under the microscope ; 

 though twenty-six hours out of the water, flagella were moving every- 

 where (though not quite on all cells). The absence of collars and 

 hemispherical outline of the cells has been described in the paper 

 referred to. The remainder of the sponge was placed in the aquarium 

 circulation, and on February 8th, at 6 p.m., was found in the most 

 healthy life, most of the cells being collared and perfectly normal in 

 shape, while the flagella were in active motion. 



(2) Some of the same collection were taken from the bottle at 

 8.30 p.m. on February 7th and placed in sea-water, having endured 

 some thirty-four hours' sojourn in air. Another experiment being 

 designed, the sea-water was saturated with indigo-carmine, was out of 

 the circulation, and through a disconnection of the tubes was most of 

 the time entirely without aeration. Notwithstanding that these cir- 

 cumstances were most unfavourable to recuperation, one of the sponges 

 examined at 4 p.m. on February 8th showed a fair proportion of collars, 

 had very active flagella all over, and looked exceedingly healthy ; 

 another examined on February 10th, though having no collars, showed 

 healthy flagellate action everywhere. Of the four other specimens 

 treated in the same way and examined on these two days, only one 

 (on February 10th) was found to be completely dead. 



(3) Some sponges were collected from the upper and exposed 

 surfaces of rocks, where rain had been falling on them for three hours. 

 They were placed in a dry bottle and, after a further three hours, 

 examined with the following results : — 



(«) Possibly dead ; no changes recognisable ; all the cells amoeboid 

 in form. 



(h) Flagellar action observed and (?) the regeneration of a collar. 



(c) Violent flagellar action. This sponge was only just dipped in 

 the sea-water before cutting, (a) and (b) had lain in sea-water some 

 minutes. 



