436 Dr. G. C. Wallich on Amoeba villosa 



for their reception. In the case of insoluble substances — such as 

 particles of mineral matter, many of which effect an entrance into 

 the enclosarc of the Amcebans, either along with alimentary 

 matter or accidentally — the vacuolar cavity is not necessarily 

 present, but the atom simply rests within the protoplasm. In 

 A. villosa the food- vacuoles are generally observable, although 

 with difficulty when the body is much distended by extraneous 

 substances and endogenous organic granules. In some speci- 

 mens they are very strikingly developed. For these vacuoles I 

 propose the term food-vacuoles, in contradistinction to the simple 

 vacuoles which form and disappear spontaneously within the 

 protoplasmic substance and, when in such great numbers as to 

 impart an almost parenchymatous character to portions of the 

 structure, apparently forebode its disruption or death. 



From the manner in which the food-vacuoles are formed at 

 the surface — in Amoeba by the coalescence of pseudopodia which 

 envelope the object about to be incepted, and in Actinophrys, by 

 the projection of a coarse irregular network of ectosarc, aided by 

 the coalescence of the pseudopodia in the immediate vicinity — 

 it would appear that a certain quantity of the surrounding water 

 is always admitted into the newly formed cavity. This water is 

 probably essential to the due performance of the digestive process, 

 and in part enters into the composition of the alimentary fluid. 

 On the other hand, it is probable that, in certain cases, a portion 

 of the water becomes absorbed by endosmosis, without under- 

 going chemical change, more especially where the food-particles 

 have been completely dissolved through the digestive process. 

 In this condition, the vacuoles may frequently be seen sharing 

 in the pseudocyclosis, till by slow degrees they entirely dis- 

 appear, — the effete watery particles, as I have already stated, 

 being then poured exosmotically into the contractile vesicle, and 

 ultimately discharged. 



In my previous notice I drew attention to the highly deve- 

 loped membranous capsule within which the nucleus of A. vil- 

 losa is contained. According to Carpenter (the latest authority 

 on the subject)*, the nucleus of Amoeba presents "the aspect of 

 a clear flattened vesicle surrounding a solid and usually spherical 

 nucleolus, and is adherent to the inner portion of the ectosarc, 

 and projects from it into the general cavity/'' Carter also de- 

 scribes it " as an organ situated on the outer portion of the 

 sarcode, which, when well marked, presents under the micro- 

 scope the appearance of a full moon (to use a familiar simile), 

 with similar slight cloudiness." He adds, " It is discoid in 

 shape, of a faint yellow colour, and fixed to one side of a trans- 



* Introduction to the Study of the Foraminifera, London, 1862, p. 24. 



