242 



BIOLOGY OF THE PROTOZOA 



many cases a portion of the old cells is left iniused or not included 

 in the protoplasm of the offspring. Thus in Plasmodium vivax 

 and other malaria organisms, the pigmented granules (melanin) are 

 left behind when the agametes separate (Fig. 120) ; in many coccidia 

 the agametes are oriented in respect to such residual products. 

 Multiple fli^'ision is also characteristic of the developing zygotes of 

 gregarines and ha?mamoebida?, the eight sporozoites of gregarines 

 and the multitude of sporozoites of Plasmodium being formed in 

 this manner. 



""ALLet"' 



ABC 



Fig. 120. — Malaria organisms. A, Plasmodium vivax in Ijlood corpuscle; B, same 

 in agamete formation with distributed melanin (m). C, Plasmodium, malarice, 

 agamete formation with concentrated melanin, c, red blood corpuscle; m, melanin; 

 n, nuclei; p, parasite; v, vacuole. (After Calkins.) 



In the above account of the reproductive activities of the Protozoa 

 no attempt has been made to give an exliaustive treatment, but 

 other examples will be given in the following chapters on classifica- 

 tion. 



In many cases in the above description there is evidence of 

 reorganization of the protoplasm and evidence that may be inter- 

 preted as su})p()rting Child's view of de-differentiation as an offset 

 to the accumulation of products of metabolism which hamper 

 further metabolic activities (p. 208). Some of this evidence is 

 given in connection with the phenomena of equal division, partic- 

 ularly in division of the ciliated forms and the conclusions reached 

 are in agreement with Child's. Hartmann, also, comes to a similar 

 conclusion in connection with the cultural history of Eiidorina 

 elegans (1923) and from merotomy experiments with Amoeba poly- 

 podia (1924). In the latter an individual was cut in two fragments; 

 the nucleated part regenerated but instead of permitting it to 

 divide it was cut again when fully grown. This process was repeated 

 until the original amoeba had been cut 32 times in forty-two days 

 and without an intervening division. The control amoebae from 

 the same clone divided 15 times in the same ])eri<)d. This experi- 

 ment would a])pear to confirm Child's argument that amputation 

 of a part of the differentiated protoplasm would effect a partial 

 rejuvenescence, and Hartmann interprets it in this way: "Repro- 



