^■38 PROFteSSOR E. RAY LANKfiSTER. 



xanthophylls and lichnoxanthines can effectually act as 

 screens than that other green pigments of a different nature 

 can play that part. 



Mr. Geddes has not adduced spectroscopic evidence simi- 

 lar to that given by Sorby in relation to Spongilla, in favour 

 of the view that the green pigment of Convoluta Schultzii is 

 caused by a mixture of blue and yellow chlorophyll, xantho- 

 phyll and lichnoxanthine, or by any one or two of these 

 bodies; nor has the precise structural form in which the 

 pigment occurs in Convoluta Schultzii been described, so that 

 Ave can compare it with the chlorophyll bodies of plants. 



PliYsiological evidence in favour of the assimilation of the 

 green pigment of Hydra ziridis to that of green plants 

 was obtained two years ago by Mr. J. E. Blomfield, of 

 Magdalen College, Oxford, and University College, London. 

 He has kindly supplied me with the following account of 

 the experiments made by him : 



*^ A number of Hydra viridis (some forty or fifty) were 

 placed in a test-tube, and the test-tube filled wiih water was 

 inverted over water in a basin, the bottom of which was 

 lined with clay so that the test-tube could be pressed into it 

 {7iot so as to completely close the tube) and maintained in 

 an upright position, and the Hydra3 could either crawl up 

 the tube or remain resting upon the clay. Any gas given 

 off from the Hydrse would necessarily ascend in the tube 

 and collect at the top of it, expelling a corresponding volume 

 of water from the inverted mouth of the tube. On exposing 

 several tubes thus prepared to direct sunlight minute bubbles 

 appeared on the Hydrse and on the side of the tube, which 

 ascending formed a large bubble at the top of the latter. 



" A test-tube containing nothing but water will, when 

 exposed to direct sunlight, be found to have its sides dotted 

 with minute bubbles, which collect into a larger bubble on 

 rising to the top of the column of liquid, but the gas so 

 separated is reabsorbed token the temperature of the tcater 

 falls from the point which it has reached by the heating 

 effect of insolation. 



''Several test-tubes containing Hydras were set up in this 

 way and left for a week, but owing to the unfortunately 

 small amount of direct sunlight at the time, only a small 

 bubble of gas was obtained at the top of each tube. The 

 bubbles so obtained were passed from the collecting tubes 

 into a smaller test-tube for analysis. The small lest-tube 

 containing some water and the collected gas was inverted 

 over mercury, and a solution of pyrogallic acid in KHO vi'as 

 introduced into the lube. One third of the total volume of 



