460 MB. HAROLD WAGER ON THE 



The Vacuole System and Gullet. 



At the anterior, colourless end of all species of Euglena and 

 allied genera there is a sharply defined S2:)ace, which was known 

 to Ehrenberg, and has been described by Klebs * as the " prin- 

 cipal vacuole," into which open one or more pulsating vacuoles t. 

 In Euglena viridis there is only one pulsating vacuole, but in 

 other species there may be two or more, and in some cases the 

 single pulsating vacuole is formed by the fusion of several 

 smaller ones %. The principal vacuole possesses the power of 

 slowly contracting, by which the liquid contained in it is dis- 

 charged ; but it is not to be regarded as a true contractile 

 vacuole, but rather as a reservoir for liquid ; and as a part of 

 this liquid is poured into it by the true pulsating vacuoles, it 

 would probably be better to describe it as an " excretory reservoir." 

 The gullet is a conical or tube-like depression in the blunt 

 anterior end of the cell, and it is usually described and figured 

 as terminating in the neighbourhood of the excretory reservoir, 

 from which it is separated by a thin layer of protoplasm only. 



According to the view at present held, the excretory reservoir 

 discharges its contents into the gullet through an opeuing which 

 is made, at the moment when the contraction begins, by the 

 rupture of the thin layer of protoplasm which separates the 

 reservoir from the gullet §. Klebs ||, however, states that no 

 opening can be observed in the excretory reservoir ; it always 

 remains sharply defined, and its slow contraction shows that such 

 an opening is improbable. 



I found, however, upon a careful examination of Euglena 

 viridis, that, contrary to the observations described above, there 

 is a permanent communication between the excretory reservoir 

 and the gullet. This is not easy to observe in the liviog cells, 

 but is very clearly seen when they are placed in a half to one 

 per cent, solution of osmic acid for several hours, or even days, 

 then mounted in dilute glycerine and observed under a ^^ih inch 

 oil-immersion objective, with the aid of a good sub-stage 

 condenser. 



* Loc. cit. p. 24G. 



t Carter, " Additional Notes on the Freshwater Infusoria in the Island of 

 Bombay," Ann. & Mag. Nat. Hist. ser. 2, vol. xx. p. 34. Stein, I. c. 

 \ Klebs, I. c. 

 § Traite Zool. Concrete, i. p. 346. 



II Loc. cit. p. 248. 



