128 Dr. G. C. Wallich on the Value of 



of these organisms leads me to the conclusion that nothing ana- 

 logous to a pellicle exists, save during the period of encystation 

 — for a similar reason that it would be unwarrantable to regard 

 the capsule within which any of the other Protozoa are enclosed 

 during their encysted condition as a true envelope belonging to 

 the creature at all times. I may repeat that I have completely 

 failed to render a membrane apparent even under the use of the 

 customary chemical reagents. By employing iodine and sul- 

 phuric acid, I have coloured the external layer to some depth at 

 times, and, as shown by Auerbach in his A. bilimbosa, have 

 caused the granular and other contents to shrink towards the 

 centre of the organism. But surely it demands much stronger 

 evidence than is derivable from this experiment, to prove that 

 the appearances so engendered are the exponents of a normal 

 condition that previously existed, and not mere eflFects of chemical 

 action on organic matter. 



With due deference to M. Auerbach, I entertain the belief 

 (based on appearances repeatedly seen by me in A. villosa 

 when imperfectly defined under the microscope, coupled with 

 those observed by me in the encysted specimen) that A. bilim- 

 bosa will prove to be either an encysted condition of another 

 form, or one of the Protean phases of the typical form, namely 

 A. villosa. The very striking character of the irregular portion 

 of the surface shown in Auerbach^s figure tends to confirm this 

 view. This has been my opinion ever since the encysted speci- 

 men came under my notice ; and I only hesitated to publish it 

 in the hope of obtaining the encysted form of A. villosa in suffi- 

 cient quantity, and with sufiicient evidence of its being a trans- 

 itional condition, to enable me to speak more confidently on the 

 subject. Meanwhile I would simply direct attention to the fact, 

 admitted by Mr. Carter, that the existence of the " pellicula " 

 (except in those cases in which chemical reagents are employed) 

 is wholly hypothetical, — and hence that the phenomena said to 

 take place in it are equally so. 



But my view with regard to A. bilimbosa is not an unsupported 

 one ; for, in order to put it to some degree of test, I have insti- 

 tuted the following experiments within the last two days. 



Having killed some Amoeba by holding a portion of the ma- 

 terial containing them in a watch-glass over a spirit-lamp, I 

 placed them under the microscope. The specimens were 

 then motionless, and devoid of the usual contractile vesicle, 

 but otherwise they scarcely differed in aspect from the living 

 specimens. I now broke them up by carefully graduated 

 pressure ; and, by a slight displacement of the thin glass cover 

 beneath which they were being examined, the detached masses 

 were separated from each other. On dilute sulphuric acid and 



