ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 357 



tion varies, and is feeble for lactose ferments. Glucose is fermented 

 1 • 6 times more quickly tLau galactose by acclimatised yeasts. Acclima- 

 tisation is gradually lost if sugar, other than galactose, lactose, or meli- 

 biose, be offered to the yeast, and if multiplication be favoured this may 

 happen in a few hours. The morphological characters of the yeasts are 

 in no way altered by acclimatisation. Certain substances (boric acid, 

 toluene) may prevent acclimatisation without preventing the fermenta- 

 tion of glucose. Alcohol is more harmful to the fermentation of galac- 

 tose than to that of other sugars. When a yeast has lost its zymase by 

 cultivation in a medium rich in pepton, it cannot be acclimatised to 

 galactose until it has been revived with glucose ; but if it has been 

 previously acclimatised it can be revived on galactose. Yeast may 

 become acclimatised to galactose in presence of glucose, and also in 

 presence of levulose, but only with difficulty. With certain yeasts the 

 process of acclimatisation is accompanied by a greater secretion of 

 melibiase or of lactase. During the process of acclimatisation only one 

 zymase undergoes a change of constitution, and this change is attended 

 by profound alteration in the constitution of the protoplasm. The 

 phenomenon of acclimatisation is, in this case then, a profound molli- 

 fication of the condition of the cell induced by a carbohydrate closely 

 allied to glucose. Finally, reference is made to the acclimatisation of 

 leucocytes to toxins and toxin substances, and a comparison is made be- 

 tween the yeast ferments and antitoxins, which latter not only accustom 

 the leucocytes to toxins but also act as the antidote. 



Rancidity of Butter.* — The more important results of an investiga- 

 tion as to the causes of butter becoming rancid carried out by Herr R. 

 Reinmann, may be summed up shortly as follows. 



There does not appear to be any relation between the rancid taste and 

 odour and the quantity of free acids formed in butter. The greater the 

 amount of casein and of milk-sugar in butter, the more quickly does it 

 become rancid. Ligbt and air (oxygen) do not appear to exert any 

 direct influence. Butter made from sterilised cream will rarely become 

 rancid, but if brought into contact with rancid butter will turn in a few 

 days. At the present time the data for determining whether rancidity is 

 due to microbes or enzymes are insufficient. 



7. General- 



New Theory of Mynnecophilous Plants.f — From observations made 

 during a stay in South America, Dr. L. Buscalioni and Herr J. Huber 

 doubt the correctness of the ordinary symbiotic theory of myrmeco- 

 philous trees and shrubs, viz. that the ants protect the plant against the 

 attacks of other injurious insects, especially leaf-cutting ants. They 

 find these species to abound especially in localities which are frequently 

 submerged by floods, where leaf-cuttiDg ants do not exist. This is par- 

 ticularly the case with species of Cecropia. The authors believe that 

 tbe habit is simply one for the advantage of the inhabiting ants them- 

 selves, and that the myrmecophilous habit is confined to species which 

 inhabit localities liable to be flooded, or which have been at some previous 

 period liable to be flooded, or to species descended from those which 

 inhabit such localities. 



* Centralbl. Bakt. u. Par., 2" Abt, vi. (1900) pp. 131-9, 166-76, 209-14. 

 t Beih. z. Bot. Centralbl., ix. (1900) pp. 85-8. 



