REPRODUCTION 239 



conclusion in connection with merotomy experiments on Amoeba 

 polypodia (1924). In the latter an individual was cut in two frag- 

 ments; 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 ameba had been cut 32 times in forty- 

 two days and without an intervening division. The control ame- 

 bae from the same clone divided 15 times in the same period. This 

 experiment would appear to confirm Child's argument that amputa- 

 tion of a part of the differentiated protoplasm would effect a partial 

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

 duction," he says, may rightly be interpreted as a process of reju- 

 venation. Our continued amputations in these experiments provide 

 a substitute for the rejuvenating effect of reproduction (1924, 

 p. 458). His further conclusion that his results "indicate experi- 

 mentally, a potential immortality of the protozoan individual" 

 (p. 456) can scarcely be allowed on the basis of forty-two days' 

 experience. A single individual of Urolcptus mobiJis has lived for 

 more than ninety days without dividing, and similar but younger 

 individuals have been cut as in Hartmann's experiments, to find out 

 if ciliates would sustain Child's conclusion. The results (not pub- 

 lished) were invariably negative, although Uroleptus is an excellent 

 type for this kind of work and invariably undergoes rejuvenescence 

 after conjugation and after endomixis (see Chapter VIII). 



With unequal division by budding and multiple division there is 

 further evidence of reorganization with reproduction. The small 

 cells that are budded off contain none of the differentiated cellular 

 elements of the parent organism. The spores are likewise provided 

 with protoplasm whose activities are unhampered by accumulated 

 products. This is clearly evident in the asexual reproduction of 

 Plasmodium vivax (p. 238), and is well illustrated in forms where 

 specialized structural elements are indications of the differentiations 

 which the old protoplasm has undergone. Thus in Mycetozoa 

 some of the hundreds of nuclei degenerate and give rise to spiral 

 elaters which with their spiral walls are made up of microsomes and 

 kinetic elements (Strasburger, Kranzlin), while parts of the proto- 

 plasm become differentiated into encrusting peridia and supporting 

 capillitia. All of these differentiations are left behind when the 

 spores are formed and distributed. Analogous somatic structures 

 are also characteristic of the spore-forming stages of some types of 

 Gregarinida and Myxosporidia. In the former the spore-contain- 

 ing organs are either relatively simple spore cysts as in Monocystis 

 types (Fig. 213, p. 531) or more complicated structures— sporangia — 

 of some polycystid gregarines (e. g., Echinomera hispid a or Gre- 

 garina cuneata). In the former the spores are dispersed by the 

 formation of gas which bursts the cyst membranes. In the latter, 

 finger-formed tubes are developed from the peripheral protoplasm 



