Dr. Wallicli on the Rhizopods. 325 



more potent tlian mine has spoken on the same subject, and 

 in words too pregnant with meaning and truth to be dis- 

 puted. I allude to Prof, Tjndall, who writes as follows : — 

 " Have the diamond, the amethyst, and the countless other 

 crystals formed in the laboratory of nature and of man no 

 structure ? Assuredly they have ; but what can the micro- 

 scope make of it ? Absolutely nothing. It cannot be too 

 distinctly borne in mind that between the microscope and the 

 true molecular limit there is room for infinite permutations 

 and combinations. It is in this region that the poles of the 

 atoms are arranged^ that tendency is given to their powers^ so 

 that lohen poles and powers have free action^ proper stimuli, 

 and a suitable eniironmentj they determine first the germ and 

 afterwards the complete organism.'''' — Fragments of Science, 

 London (6th edit.), 1879. 



It only remains for me to point out that attention was not 

 invited to the ^' potentialities " of organization in the sarcodic 

 bodies of the Rhizopoda, with a view of bringing them to 

 bear on the questions we are now engaged in investigating, 

 but solely to show that the existence of these potentialities 

 ought to be recognized, although for the present we must rest 

 content to avail ourselves of such characters as are made 

 palpable to our senses with the aid of the microscope. 



This being clearly understood, let me observe that no 

 satisfactory evidence has as yet been discovered of any generic 

 difference between the animal we call Amceha and the animal 

 we call a Biffiugia beyond the palpable one which hinges on 

 the fact of the former being a naked and the latter a testaceous 

 Rhizopod. The sarcode-body in both presents the same degree 

 of differentiation into what is known as endosarc and ectosarc. 

 In both it is provided with a nucleus and contractile vesicle. In 

 both there is a definite anterior and posterior part, the function 

 of the latter being to exercise a certain degree of prehensile action, 

 that is to say to the extent of regulating the movements of the 

 body in the naked forms and maintaining its position within 

 the test in the testaceous ones. In both there occur sarco- 

 blasts, oil-globules, and crystalloids ; and in both we may 

 observe extensive vacuolation and the gradual development 

 of a membranous investment of the entire body-substance 

 when encystation is about to take place. 



But if outward characters are to be taken at all as our 

 guides, the identity of the two animals in Amoeba and Difflu- 

 gia can be shown in a still more striking manner. Thus it 

 frequently happens that a Difflugian Amceha will vacate its 

 test whilst under observation, and sally forth as a naked 

 Amoeba without appearing to have sustained any injury or 



