464 Dr. G. C. Wallich on the Distinctive Characters, Habits, 



renders it certain that the presence of the diatoms is in no 

 manner connected with their encystation or reproductive pro- 

 cesses. 



Assuming then, as I believe there is every reason for doing, 

 that the Amoeban Rhizopods are hermaphrodite, but leaving 

 for future and much more extended research the determi- 

 nation of the male and female elements, with the precise method 

 in which the impregnation of the latter is effected, I think we 

 are fully warranted in recognizing the operation of no less 

 than three apparently distinct modes in which a new brood 

 may be developed, and in regarding this singular feature in 

 their history as a provision for the perpetuation of the species, 

 without reference to the stage of development at which the 

 parent may have arrived when it happens to be destroyed. 



The following are the three modes of reproduction in ques- 

 tion : — 



I. By extrusion from the body of the parent of a minute indi- 

 vidual already perfect as regards the essential characters of the 

 species. 



II. By development, singly, from one of the sarcoblasts, or 

 acapsular nuclear masses, which are formed within the body of 

 the parent either prior to or during the process of encysta- 

 tion, 



III. By development, singly, from each of the granules of 

 the acapsular nuclear masses, on the disruption of the latter. 



Whilst the multiplication of the individual, or, to speak more 

 correctly, the vegetative repetition of the species, may be brought 

 about, 



I. By the disruption of the parent body into two or more 

 parts, each capable of maintaining an independent existence. 



II. By gemmation, or the evolution, from some portion of the 

 surface of the parent, of a " geramule,^^ destined ultimately to 

 assume the characters of the species. This last process I am 

 unable to vouch for on my own authority, except as regards 

 Actinophrys. 



Assuming, then, that the evidence adduced throughout the 

 previous and present communication establishes the fact that the 

 differentiation into ectosarc and endosarc is of the kind indi- 

 cated — that is to say, a process involving the increased consolida- 

 tion of the external layer by the operation of physical agencies 

 on living sarcode, whilst the reconversion of this external layer, 

 and the constant interchange taking place between it and the 

 more fluid mass within, coupled with its inherent contractility 

 and extensibility, are the essential attributes of this substance — 

 is it possible to account for the appearances attending the incep- 

 tion and extrusion of foreign matter, the fox^mation of vacuolar 



