988 SUMMARY OF CURRENT RESEARCHES RELATING TO 



it is suggested, be applied advantageously in the study of the diges- 

 tion of the Infusoria, of the movement of diatoms and ciliated 

 organisms, &c. 



Apparatus for Aerating Aquaria.* — Different forms of apparatus 

 are used in laboratories for supplying air to plants and animals kept 

 for observation in aquaria. These, P. Francotte thinks, are all rather 

 complicated, and he has therefore constructed two very simple models, 

 which he has successfully employed. 



Make a loop at 30 cm. from one of the extremities of a glass 

 tube of from 5 to 7 cm. diameter and 1 m. long. To do this heat 

 the tube and bend it on itself, the tube thus being divided into two 

 uneqiial portions. 



At 7 or 8 cm. from the loop, and in the shorter part of the tube, 

 heat a small point by the blow-pipe. The heated glass forms a little 

 bead, and whilst this is very hot draw it out (by a piece of tubing) 

 into a little capillary tube, and bend it if possible at a right angle at 

 a distance of 1 cm. from its point of origin, at the same time breaking 

 off the end. The tube, thus prepared, is put in communication with 

 a vessel of some litres' capacity, placed at a height of from 1 m. to 

 1 • 50 m. This can be done by a piece of indiarubber tubing and a 

 siphon, the short arm of which is immersed in the vessel. By sucking 

 the lower end of the tube, the latter will be filled with water. The ■ 

 liquid column will play the part of a piston in a pump ; the air will 

 be drawn through the opening of the capillary tube, and a number of 

 little columns of water will be produced containing between them 

 bubbles of air. 



To regulate the flow of water and insure the air being supplied in 

 proportion to the liquid used, the indiarubber tube should be com- 

 pressed by a clip, and the apparatus made to work as slowly as 

 possible, so that the air-bubbles drawn in can be easily counted. 

 The lower extremity of the tube is plunged in the aquarium, w^here 

 the air causes a bubbling and movement in the water. 



Dr. Fol recently suggested f saturating with carbonic acid the 

 sea-water containing Medusse, star-fishes, &c., in order to render 

 them motionless. This can be best accomplished by a modification 

 of the above apparatus. In place of drawing out a. capillary tube, a 

 tube of the same diameter as the principal tube is soldered at right 

 angles to it and slightly bent. The branch tube is then by an india- 

 rubber tube placed in communication with the apparatus containing 

 the gas, ether, &c. 



Detection of Sewage Contamination by the use of the Micro- 

 scope, and on the Purifying Action of minute Animals and Plants.:}:— 

 Dr. H. C. Sorby writes : " By studying with the Microscope the solid 

 matters deposited from the waters of a river, the previous contamina- 

 tion with sewage can usually be detected without any considerable 

 difficulty. If the amount be serious, the characteristic particles of 



* Bull Soc. Belg. Micr., x. (1884) pp. 141-3. 



t See this Journal, iii. (1883) p. 137. 



X Jouru, Soc. Arts, xxxii. (1884) pp. 929-30. 



