Chapter IV 

 KINGDOM PROTOCTISTA 



Kingdom !l. PROTOCTISTA Hogg 



Regne Psycho diaire, Psychodies, Bory de Saint Vincent Diet. Class Hist. Nat. 8: 

 246 (1825), 14: 329 (1828). 



Kingdom Protozoa Owen Palaeontology 5 (1860), not class Protozoa Goldfuss 

 (1818). 



Regnum Primigenium seu Protoctista Hogg in Edinburgh New Philos. Jour. n.s. 

 12: 223 (1860). 



Kingdom Acrita or Protozoa Owen Palaeontology ed 2: 6 (1861). 



Kingdom Primalia Wilson and Cassin in Proc. Acad. Nat. Sci. Philadelphia 1863: 

 117 (1864). 



Kingdom Protista Haeckel Gen. Morph. 2: xix (1866). 



Kingdom Protobionta Rothmaler in Biol. Centralbl. 67: 243 (1948). 



Nucleate organisms other than Plantae and Animalia: the marine algae and the 

 fungi and protozoa. Amiba diffluens may be construed as the standard. 



The name Protista, of Haeckel, is the most familiar among those which have been 

 applied to the kingdom here to be discussed, but it is not the earliest. Among fol- 

 lowers of Cuvier, the animal kingdom consisted necessarily of four branches. Presum- 

 ably, it was this tradition that induced Owen to refer the Infusoria and Amorphozoa 

 (sponges) to a separate kingdom, which he called Protozoa. A year later, Owen pub- 

 lished an alternative name for this kingdom; but Hogg had already published modi- 

 fications of two of Owen's names, Protoctista and Amorphoctista(KTi^co,to establish, 

 create), for the reason that names in -zoa appeared inappropiiate to groups excluded 

 from the animal kingdom. 



The limits here given to the kingdom Protoctista were proposed by the present 

 author (1938, 1947). They have been accepted, with exception in a single significant 

 point, by Barkley (1939, 1949) and Rothmaler (1948). 



It is assumed that the evolutionary origin of the Protoctista consisted of the evolu- 

 tionary origin of the nucleus, and that all nuclei are essentially the same thing. Kofoid 

 (1923) insisted that enduringly viable nuclei originate among protozoa, as among 

 plants and animals, regularly by mitosis, never by binary or multipe fragmentation, 

 nor by aggregation of stainable granules. He did not recognize the nucleus as essen- 

 tially a device for sexual reproduction. Several considerable groups of protozoa, how- 

 ever, which Kofoid listed as not known to reproduce sexually, have been found to 

 do so. Here, then, it is maintained that all nuclei, in this kingdom as among plants 

 and animals, are the same thing; and that the nucleus is essentially a device for sexual 

 reproduction, that is, for processes of reproduction which involve always one act of 

 meiosis and one of karyogamy, and which produce Mendelian heredity as an effect. 



Photosynthesis is believed to have evolved only cnce. As it occurs both among non- 

 nucleate and nucleate organisms, the nucleus is believed to have evolved in organisms 

 living by this function. The closest approach between non-nucleate and nucleate or- 

 ganisms is believed to be between the blue-green algae and the primitive red algae 

 (Smith, 1933; Tilden, 1933). Thus it appears that the original nucleate organisms 

 were not capable of swimming by means of flagella. Flagella appear to have evolved 

 in unicellular nucleate photosynthetic organisms as a device for dissemination (Bes- 



