586 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



centre in a ridge 0*05 m. high, and this ridge surrounds a circular 

 opening b, which furnishes a communication between the two parts of 

 the apparatus. It is in the cylinder A that the vessels are placed in 

 which the cultures are made. This being done, a small packet of about 

 5 grin, of pyrogallic acid in filter-paper is introduced through the 

 opening b into the bottom of the bell-glass. The latter is then applied 

 to the cylinder. The whole apparatus is then inclined, so that the 

 highest part of the floor of the bell-glass is that on which rests the 

 packet of pyrogallic acid. This position is maintained by means of a 

 block of wood (fig. 93). The stop-cock is then removed, and by means 

 of a funnel, the stem of which is suitably bent, about 100 c.cm. of a 

 10 p.c. solution of caustic potash are introduced into the bell-glass in 

 such a way that, thanks to the inclination, none of it touches the pyro- 

 gallic acid. The stop-cock is then replaced and the air exhausted. When 

 the rarefaction has reached a maximum, the stop-cock is closed, and the 



Fig. 92. 



Fig. 93. 



apparatus placed in a horizontal position, the latter causing the mixture 

 of the acid with the potash solution. Thus the traces of oxygen left 

 after exhaustion of the apparatus are absorbed by the pyrogallate of 

 potash. Before placing in the incubator the author recommends that 

 all the apposed glass surfaces of the apparatus should be covered with 

 a mixture in equal parts of wax and vaselin. This renders it more 

 surely air-tight. 



Pure Cultures of Chlorella vulgaris.*— E. Herouard obtains pure 

 cultures of this alga on potato. Obliquely cut cylinders of the medium 

 are placed in test-tubes having a constriction near the lower end. At 

 the bottom of the tube is placed a little water, or a mixture of water 

 and 10 p.c. glycerin. The tube is plugged with cotton-wool and 

 sterilised in the autoclave. The sterilisation should be lengthy or 

 repeated on several occasions. The medium should be inoculated with 

 the usual precautions, and care should be taken to spread the seed over 



* Bull. Soc. Zool. de France, xxix. (1904) pp. 110-4. 



