102 



THE CELL AND PROTOPLASM 



ment of mouth, axostyle, undulating mem- 

 brane, and parabasal body, and aach cease- 

 lessly struggles to rid itself of its encum- 

 bering mates. There is no unity in this 

 multicellular phase of Trichomonas. But 

 in Giardia, a two-celled bilaterally sym- 

 metrical organism with 4 pairs of flagella, 

 there are 2 permanent cross commissures in 

 its fibrillar system, and these afford a struc- 

 tural and functional coordination of the two 

 constituent cells so complete that no rever- 

 sion to the one-celled stage is known. No 

 sexual reproduction is known and fission 

 merely reproduces the parent two-celled 

 stage. 



Another superstition widely counte- 

 nanced in elementary textbooks, seemingly 

 for purposes of enhancing the evolutionary 

 outlook, is the mistaken idea that the Pro- 

 tozoa are simple in structure as well as uni- 

 cellular. It is true that an amoeba or a 

 monad is relatively quite simple, but so was 

 a vertebrate egg prior to the discovery of 

 organizers. As a matter of fact, every class 

 of protozoans has evolved into great com- 

 plexities of structure. Evidences of this are 

 seen in the remarkable diversifications of 

 flagella among the flagellate parasites of 

 termites, showing enormous increase in 

 number, up to thousands ; diversification of 

 structure into internal axostyles, rods, and 

 spirals, and external flagella of different 

 orders, sizes, and structures; repeated sets 

 of neuromotor equipments without at- 

 tendant nuclei, nuclear multiplication, and 

 the evolution of various structural types of 

 multicellular bodies. Space does not permit 

 a discussion of the elaboration of skeletal 

 types in the Radiolaria and Foraminifera, 

 of skeletal and flotation devices in the Dino- 

 flagellata, and of fibrillar neuromotor sys- 

 tems in the Ciliata. Truly, the Protozoa are 

 indeed far from simple. 



Now two significant features mark these 

 differentiations among the protozoan organ- 

 isms. The first is that many of them occur 

 within the limits of a single cell. A single 

 striking example of this is seen in that re- 

 markable dinoflagellate, Erythropsis, an 

 organism so unique that when R. Hertwig's 

 description was published in 1884 the ven- 



erable Carl Vogt, in 1885, came out with a 

 tirade about the unwarranted "wissen- 

 schaf tliche Irrthum ' ' in which a young un- 

 named docent had found a Vorticella that 

 had eaten the eye of a rotten medusa, and 

 had foisted upon the biological world a 

 scientific lie which as Lord Bacon long ago 

 said would ride ahorseback while truth 

 would lag behind afoot. 



This Erythropsis has not only the custom- 

 ary transverse low-spiraled girdle with its 

 included transverse flagellum and its pos- 

 teriorly directed longitudinal flagellum, but 

 it also has a contractile tentacle with circu- 

 lar and longitudinal muscle fibrils or myo- 

 nemes, and, as its name indicates, a red eye 

 composed of a laminated lens, a mobile 

 black pigment mass, and a red core, pre- 

 sumably the sensory organelle. It is car- 

 nivorous, even cannibalistic, in feeding 

 habits, and mirabile dictu, has but a single 

 nucleus. Some of the related holozoic dino- 

 flagellates have nettling organelles or nema- 

 tocysts of patterns comparable to those in 

 the Coelenterata, but the whole organism is 

 the cnidoblast. 



Colony formation is rather widely preva- 

 lent among the Dinoflagellata. In its sim- 

 plest and more widely prevalent form this 

 is merely chain formation in which new 

 individuals are formed by repeated di- 

 visions putting daughter cells in place of 

 the mother cell. These chains usually are 

 temporary and soon break up into the con- 

 stituent individual organisms or cells. 

 They are most abundant in the marine 

 plankton about 4 a.m., for fissions occur 

 generally before daybreak. 



One naked or unarmored dinoflagellate, 

 Polykrikos, habitually is found only in the 

 stage of a linear body of 2, 4, or 8 cells. 

 The ventral longitudinal furrow of each is 

 continuous with that of its neighbors, thus 

 forming for the organism a long ventral 

 mouth whose borders are plastic and send 

 out pseudopodia. By means of this large 

 mouth the organism captures other dino- 

 flagellates and metazoan ova as food, and 

 does it indifferently with 2, 4, or 8 cells. 

 The cytoplasm contains numerous nemato- 

 cysts formed by repeated outgrowths of the 



