OF THE PROTOZOA. RHIZOPODA. 213 



of Amoebce, often displayed when, by a fracture of the shell, the animal con- 

 tents escape. The nucleus has the form of a thick-walled sac, and encloses a 

 large nucleolus. But it is remarkable that, whilst one or at most two nuclei 

 only are discoYerable in Amoebce, several such organs are frequently present 

 in ArceUce, theu^ number being in direct proportion with the magnitude of the 

 animals. In large specimens, of i'" in diameter, above 40 such nuclei have 

 been encountered. 



Reproduction of Rhizopoda. — This function is not satisfactorily made out, 

 especially in the case of the Foraminifera ; what is known will best be de- 

 tailed of each family separately. 



Among the Amoebina self-division has been noticed by Ehrenberg to occur 

 in t\iQ Amceba prince])s; and Dujardin remarks that '^ they may doubtless 

 multiply by spontaneous fission, or by the thi'o^ving off a lobe which imme- 

 diately commences an independent existence." This separation of a portion 

 of their substance is not unusual, as, when a large variable process has been 

 shot out far from the chief mass and become enlarged at the extremity, the 

 expanded end retains its position, whilst the portion connecting it vdth the 

 body becomes finer and finer by being withdrawn into the parent mass, until 

 it at last breaks across, lea\'ing a detached piece, which immediately on its 

 own account shoots out processes, and manifests an independent existence. 

 This phenomenon is therefore one of simple detachment, and cannot rightly 

 be called a process of fission. Schneider terms it '' propagation by gemma- 

 tion," and supposes it attended by a division of the nucleus, of which every 

 such offset, in his opinion, includes a portion. This same observer fiu-ther 

 states that Amoeba has actually a " state of rest " {i. e. an encysted condition). 

 He observed it fii^st to become round, and then to form a fii^m membrane on 

 one side, whilst the other portion continued its peculiar character and move- 

 ments. By degrees the membrane extended itself over the whole body, the 

 moveable portion constantly becoming smaller, until at last a completely- 

 closed cyst was produced, in the clear interior of which a round nucleus, 

 vdih. a reddish halo, exactly like that of Polytoma and other Monaclina, 

 might be distinctly observed. He adds — " In the nucleus of Amoeba I have 

 often noticed on the outer surface of the reddish halo, granulations which 

 united to form a closed membrane, whilst at other times the nucleus exactly 

 resembled that of Polytoma " (^. e. was without an enclosing membrane). 

 What is the next phase of development following this encysted stage, 

 Schneider has nothing to show. 



If Lieberkuhn's obseiwation be correct, a most extraordinary relation sub- 

 sists between Amoebce and Oregarince, involving the existence of the former 

 as a distinct class of animated beings. This observer saw the production 

 of Amoebce from Navicellce, the origin of which from Gregarince is as good as 

 proved ; and also met with such Amoebce in eveiy transition to perfect Gre- 

 garince. This fact is alluded to in a paper by Kolliker (J. M. S. i. p. 212), 

 who behoves the AnguiUula-like animal noticed by Henle, and termed by 

 Bract Filar ia, to be an Infusorium aUied to Opalina Proteus, and goes on 

 to say that the transition of this presumed F'daria into a Gregarina- and 

 finally into a iV«y<ceW«-receptacle is nothing extraordinary. Auerbach asserts 

 the encysting process to be shared in by the Amcebcea along vath. other 

 Infusoria ; but he looks upon Schneider's recorded instance as an erroneous 

 conception of a specimen clearly enveloped by an integument. 



Monathalamia would seem capable of multiplpng themselves Hke the 

 Amoebina, by detaching portions of their substance, i. e. by a species of gem- 

 mation. Peltier has described this occurrence, although Ehrenberg failed to 

 detect it. 



