92 MEMOIRS OF THE UNIVERSITY OF CALIFORNIA 



is readr to take in another living body and brealv down an organization similar, 

 and chemically equal, to its own to render it available for its own use. 



The transition stage between these two groups must be looked for in the 

 relatively large group of flagellates not far removed from the base of the 

 phylogenetic tree. The increasing evidence points to the fact that both t^'pes 

 of niitrition, as well as the intermediate saprophytic type, are found in forms 

 otherwise closely related, and even in the same individual either at the same 

 time or under the sthnulus of different euviromuental conditions (Zumstein, 

 3899). 



This advance in feeding habits from a saproph\i;ic to a typical holozoic 

 method is foimd in parasitic as well as free-living Protozoa, and shows a corre- 

 sponding close correlation with increasing morphological differentiation. Thus 

 in the simpler t^^^e of flagellates, as in Tri/pauosoma and Prowazekia, lacking 

 a definite oral region, and living in the lymph of the blood and the intestinal 

 canal respectively, nutrition is of the saprophytic t^qje. In some of the tricho- 

 monads, as in Tetratricltomonas proirazekin (Kofoid and Swezy, 1915), a 

 definite c^i;ostome is present and food masses are ingested, showing an advance 

 to a holozoic mode of nutrition. This type of nutrition is accompanied by a 

 considerable morphological diiferentiation. 



The Protozoa also offer evidences that point to the conclusion that para- 

 sitism in this group is not always s^inbolic of morphological degeneracy, but 

 rather lies often in the upward path of the lines of structural evolution, the 

 reverse of conditions foimd in some of the ]\Ietazoa. In the Blastodiniidae we 

 find this illustrated by the tendency to form a somatella. 



In this group the life cycle, as sho's\'n in Blasfodininm pruvofi (fig. J) and 

 Chi/fn'odiuiiDii roseio)) (fig. K), l^ecomes increasingly more complex, and the 

 organism attains a larger size, than is the case in free-living forms (fig. I). 

 This condition is found to hold in many instances throughout the Protozoa 

 generally. Among the ciliates the most highly specialized forms are those be- 

 longing to the Orphryoscolecidae and living in the stomach of rimiinants, such 

 (iH Diplodiuinm (Sharp, 1914). 



Another group which presents increasing evidences of complexity in the 

 life cycle and in anatomical features, which may even be carried to the extent 

 of forming a somatella of several differentiated cells, as in Mt/xoholus (Doflein, 

 1911), is the Sporozoa. These are wholly parasitic, no free-living species being 

 kno^\^l. 



These two types of nutrition, namely, saproph}i:ic and parasitic, thus seem 

 to be stages in the natural development of the Protozoa, each marking an 

 advance along some line. AYhen these are secondarily acquired in higher forms, 

 however, as in many cases in the Aletazoa, such as the j^arasitic crustacean 

 Sdccidina, the reverse of this is true and this mode of life becomes symbolic of 

 degeneracy. 



