RECENT RESEARCHES INTO THE HISTORY OF BACTERIA. 259 



Exner, in his Leitfaden bei der mikroscopischen Unter- 

 suchungen, Leipzig, 1873, p. 64, directs that lo<ywood chips 

 are to be boiled in a concentrated solution of alum, or that 

 the wood should be boiled in water and alum added to 

 the decoction until it becomes of a fine blue colour. I have 

 not been able to discover who first used the logwood as dis- 

 tinguished from haematoxylin, nor what the original formula 

 was. Possibly the chips may succeed with more certainty 

 than the extract. After having previously obtained an 

 excellent solution with the extract I have lately had difficulty 

 in obtaining an extract that would yield a good dye, and 

 as I find other observers have found the extract bought from 

 druggists equally unreliable, I may save trouble to some 

 readers of the Journal by mentioning that a good logwood 

 dye is sold by Mr. Martindale, chemist. New Cavendish 

 Street, London, "W. 



I have to express my indebtedness to Mr. Ewart for the 

 execution of the drawings in Plate XV. 



An Account of the Recent Researches into the History 

 of the Bacteria, made by, and under the direction of. 

 Prof. CoHN.' By F. Jeffrey Bell, Exhibitioner of 

 Magdalen College, Oxford. (With Plate XX.) 



In the April number of the 13th volume of this Journal 

 (1873), an account was given of the first series of observa- 

 tions on Bacteria which Professor Cohn had published in 

 his valuable ' Beitrage zur Biologic der Pflanzen' (Heft 2) ; 

 in the 3rd Heft, published last year, the subject is continued 

 by Cohn, in addition to whom Eidam, working in his 

 laboratory, gives an account of certain experiments made on 

 these interesting organisms. Since the publication of the 

 previous paper the discussion concerning spontaneous gene- 

 ration has changed in aspect ; Dr. Burdon Sanderson has 

 given an account of several Bacterioid forms, in his Reports to 

 the Medical Officer of the Privy Council, and Professor Ray 

 Lankester has called the attention of readers of this Journal 

 to the subject by his very interesting account of " a peach- 

 coloured Bacterium." To the wide interest exhibited in these 

 forms Cohn briefly refers, but mentions at greater length 

 the work of BiHroth, published by George Reimer, of 



' ' Beitrage zur Biologie der Pflanzen,' 3es Heft, 1875. 



