1879.] Physiology and Histology o/Convoluta Schultzii. 451 



The determination of the nature of the evolved gas was readily 

 effected. On transferring the quantity produced in one or two vessels 

 to a small test-tube, and plunging into it a match with red hot tip, 

 there was to be seen the white glow characteristic of dilute oxygen. 

 A large glass tube of tolerably even calibre, about 75 centims. long, 

 was sealed at one end, and bent at about two-thirds of its length from 

 that point at an angle of 60°. It was then filled with water, and the 

 water in the long sealed arm almost entirely replaced by gas at the 

 pneumatic trough. This comparatively large quantity of gas, about 

 60 cenbims. cube, was obtained by exposing a dozen or so of apparatuses 

 exactly similar to that described, except that bell-jars, sealed funnels, 

 &c, sometimes replaced the upper flat dish, and white soup plates the 

 lower. They were set agoing about noon, and the abundant gas 

 yielded by thus exposing a surface of nearly a third of a square metre 

 covered with Planarians was collected at sunset. 



On agitating the gas with a solution of potassic hydrate a barely 

 appreciable absorption of carbonic anhydride took place, but on the 

 addition of pyrogallic acid with renewed agitation, the intense brown 

 coloration, with rapid and considerable ascent of the fluid in the long 

 arm of the tube, confirmed the presence of a large percentage of 

 oxygen. 



The results of many experiments varied from 43 to 52 per cent, of 

 oxygen ; the higher number representing the amount of gas given off 

 by freshly collected Planarians, and the lower that yielded on the 

 second or third day of their subjection to experiment. In order to 

 judge of the degree of accuracy which I could obtain by this rough 

 method of analysis, I estimated by it the oxygen of common air, and 

 obtained 19'9 per cent, instead of 20*9. Allowing for this loss of 

 about 5 per cent., it may safely be asserted that the gas evolved by 

 these animals does not contain less than from 45 to 55 per 100 of 

 oxygen. 



The Planarians are little the worse after a 24 hours' journey from 

 Roscoff to Paris, and when placed in an aquarium they instantly 

 betake themselves to the side next the window, and live there resting 

 on the bottom or clinging to the side for four or five weeks without 

 food. They certainly diminish considerably in size, yet I have little 

 doubt that they go on decomposing C0 2 and assimilating the carbon 

 even in the dull winter daylight, for when kept in darkness they 

 generally died much sooner. 



The conspicuousness of the Planarians on the sandy beach, far from 

 the shelter which rocks or algse might afford, has been already men- 

 tioned, and at first sight one is apt to think that they must be the 

 easy prey of all the larger shore-frequenting animals, and to wonder 

 that so many escape. But the observation made by Wallace and Belt 

 for so many higher animals — that conspicuously coloured forms are 



