278 



THE AMEBIC AN NATURALIST [Vol. L 



of form and structure at a very early period. 30 The 

 Mycetozoa exemplify another development of the creep- 

 ing plasmodial type adapted to a semi-terrestrial mode of 

 life. 



In the Mastigophora the body generally remains small, 

 while developing organs of locomotion and food-capture 

 in the form of the characteristic flagella. In this class 

 there is a strong tendency to colony-formation brought 

 about by incomplete separation of sister-individuals pro- 

 duced in the ordinary process of reproduction by binary 

 fission. The so-called colonies (they would better be 

 termed families) show a most significant tendency to 

 individualization, often accompanied by physiological and 

 morphological specialization of the component flagellate 

 individuals. 



As an offshoot, probably, from ancestors of the Masti- 

 gophoran type arose the Infusoria, the Cilia ta and their 

 allies, representing by far the most highly organized uni- 

 cellular type of living being. No cell in the bodies of the 

 Metazoa attains to such a complication of structure as 

 that exhibited by many Ciliates. In the Metazoa the in- 

 dividual cells may be highly specialized for some particu- 

 lar function of life; but a Ciliate is a complete and inde- 

 pendent organism and is specialized for each and all of 

 the vital functions performed by the Metazoan body as a 

 whole. From the physiological standpoint a Ciliate (or 

 any other Protist) is equivalent and analogous to a com- 

 plete Metazoon, say a man, but I can not for a moment 

 agree with Dobell 31 that the body of a Ciliate is homol- 

 ogous with that of a Metazoon— not at least if the word 

 homologous be used in its usual biological sense of homo- 

 genetic as opposed to homoplastic. Dobell appears to me 

 to negative his own conclusion when he maintains that 

 the body of a Ciliate is "non-cellular" while admitting 

 that the Metazoon is multicellular ; how then can they be 

 said to be homologous? Only if the term homologous be 



so For Foraminifera see especially Heron-Allen, Phil. Trans. (B), Vol. 

 206 (1915), p. 229. 



8i Journal of Genetics, IV (1914), p. 136. 



