334 Dr. G. C. Wallich on the Distinctive Characters and 



of Infusoria the presence of a fixed and determinate aperture or 

 apertures connected with a digestive system sufficiently separates 

 them from the Amoeban or highest type of Rhizopod structure. 



But, to revert once more to the Amoebm. Within the past 

 fortnight my friend Mr. J. N. Tomkins, the able Inspector of 

 the Government Vaccine Department, called my attention to his 

 having unexpectedly detected a profusion of Amoebce, possessing 

 all the characters of ^. villosa, in some damp confervoid material 

 which had been scraped off a stone slab in his garden and con- 

 signed to a vessel containing water, about two months previously. 

 I confess that, even putting out of the question the untenable 

 theory of " spontaneous generation/^ the development of these 

 AmcebcB from germs either constantly present in damp soil or 

 deposited on it through the medium of wind or rain from distant 

 localities was regarded by me with doubt, if not actual incre- 

 dulity. For knowing how zealously my friend collects the various 

 microscopic forms of life, it seemed far from improbable that 

 these AmoebcE were derived from the refuse cast aside from his 

 aquaria. The sequel, however, showed that my doubts were 

 altogether groundless. But, leaving this point for the present, I 

 may state that the question I was especially desirous of deter- 

 mining — namely, the possibility of a gelatinous organism like an 

 Amoeba being able to withstand the desiccation to which it must 

 be subject during summer if it be the normal inhabitant of con- 

 fervoid growth met with in similar positions — was deemed by me 

 sufficiently important to merit immediate inquiry. 



On examination of a portion of the material which had been 

 kindly placed at my command, I found it contained an abundant 

 stock of Amcebce, both old and young, and that these exhibited 

 (at a bird's-eye view, as it were) the collective characters of 

 Amoeba radiosa, diffluens, globularis, Schultzii, Umax, princeps, 

 gut tula, verrucosa, quadrilineata, actinophora, and villosa. But 

 whilst it would have been easy to select individual specimens 

 presenting in a marked degree those purely external characters 

 which have been held to distinguish all but the last-named of 

 these forms, it would have been equally easy to demonstrate, by 

 means of the infinite intermediate varieties, that all are the off- 

 spring of a common parent, and that the mere outward deviations 

 in figure and degree of differentiation are dependent on those 

 ever-varying physical conditions to which they are amenable, and 

 which will probably for ever elude our scrutiny. 



It is necessary to state explicitly that I lay no claim to the 

 discovery that many Infusoria and some even more highly or- 

 ganized forms (as, for example, Rotifera) undergo desiccation 

 without perishing. Professor Ehrenberg, Dr. B. Hicks, and 

 more recently M. Balbiani in conjunction with Mr. Samuelson, 



