Exogenous Diviswn in the Antwhan Rhizopods. 33 



artificial division is effected by the scalpel or other mechanical 

 means. 



As regards spontaneously occurring division — that is to say, 

 division effected by the mere contractility of tiie sarcode and 

 without participation on the part of the nucleus — nothing is as 

 yet known so far as I am aware. At the same time, I will 

 not undertake to say that s))ontaneous division, in the sense 

 indicated, may not occasionally take place under natural con- 

 ditions. But even should spontaneous separation take place 

 fifty times, or fifty times fifty, the process would not result in 

 "regeneration," this being impossible unless the nucleus 

 participates to such an extent as to apportion some share of 

 the fecundative granules of which it consists to each sepa- 

 rated fragment. 



Nor have we any positive information as to whether a de- 

 tached enucleate fragment of Amoeba retains the faculty of 

 digesting any food-material it may seize with its pseudopodia. 

 But if negative evidence of a very powerful and constant kind 

 is of any value, it is, I think, justifiable to assume that no 

 detached enucleate portion of the Amoeban body-substance can 

 reproduce its kind in a perfect form, or multiply otherwise 

 than by a repetition of purely unreproductive division. 



Unfortunately our knowledge of the physiological functions 

 belonging to these organisms must remain incomplete so long 

 as the extraordinary difficulties inseparable from any strictly 

 continuous examination of individual specimens from tlie 

 beginning to the close of their entire life-cycle, under condi- 

 tions not liable to interfere to any material extent with their 

 free and healthy development, remain to be overcome. Th^^se 

 difficulties, overcome as they nevertheless have been in the 

 case of much more minute organisms than the Rhizopods, 

 namely in the Monads, through the indefatigable perseverance 

 and scientific skill of Messrs. Dallinger and Drysdale, are 

 augmented rather than diminished in the case of the Amoeh(x, 

 owing to the more protracted periods occupied by these 

 organisms in passing through the various phases of their exist- 

 ence. For the present we must therefore rest content with 

 collecting, piecemeal, all facts that bear upon the subject, and 

 trust to the zeal of such competent observers as Dr. Gruber 

 to work them out to their legitimate conclusions. 



It now only remains for me to invite attention to a novel 

 means of rendering the nucleus visible in the naked Rhizo- 

 pods, and probably in the Protozoa generally, when the detec- 

 tion of this organ is rendered difficult, or even impossible, by 

 being surrounded by more or less opaque particles of different 

 kinds ; the necessity for some more efficacious way of detect- 

 Ann. cD Mag. N. Hist. Ser. 5. Vol. xviii. 3 



