86 MORPHOLOGICAL DEVELOPMENT. 



Our survey of morphological composition throughout tl 

 animal kingdom, must therefore begin with those undiffer- 

 entiated aggregates of physiological units [or constitutional 

 units], out of which are formed what we call, with consider- 

 able license, morphological units. 



§ 200. In that division of the Protozoa distinguished as 

 Rhizopoda, are presented, under various modifications, these 

 minute portions of living organic matter, so little differenti- 

 ated, if not positively undifferentiated, that animal individu- 

 ality can scarcely be claimed for them. Figs. 131, 132, and 

 133, represent certain nearly-allied types of these — Amoeba, 



i 



13/ 138 



133 



Actinophrys, and Lieberkiihnia. The viscid jelly or sarcode, 

 comparable in its physical properties to white of egg, out of 

 which one of these creatures is mainly formed, shows us in 

 various ways, the feebleness with which the component 

 physiological units are integrated — shows us this by its very 

 slight cohesion, by the extreme indefiniteness and mutability 

 of its form, and by the absence of a limiting membrane. 

 It is no longer held even by unqualified adherents of the 

 cell-doctrine that the Amceba has an investment. Its outer 

 surface, compared to the film which forms on the surface of 

 paste, does not prevent the taking of solid particles into the 

 mass of the body, and does not, in such kindred forms as 

 Fig. 133, prevent the pseudopodia from coalescing when they 

 meet. Hence it cannot properly have the name of a cell-wall. 

 A considerable portion of the body, however, in Difflugia, 



shocks, producing changes all around. In the earlier stages of cell-evolution 

 this unstable substance is dispersed throughout the cytoplasm ; whereas in 

 the more advanced stages it is gathered together in one mass. If so, instead 

 of saying there is a dispersed nucleus we should say there are the materials 

 of a nucleus not yet integrated. 



