THE NEW GENEALOGICAL TREE 359 



ship and connections that exist within the sub-kingdom 

 Protozoa. This uncertainty is met with as soon as we try to 

 solve the question of which group of the Protozoa should 

 be placed at the beginning. Naturally enough this question 

 is also connected with the problem of the origin of the 

 Protozoa. 



If we bypass the earliest studies of the Protozoa we see 

 that initially a majority of zoologists had considered the 

 Rhizopoda and the amoebae as the most primitive Protozoa 

 because they do not have a permanent external form and 

 because they develop transitional pseudopodia only. These 

 forms were considered as the initial forms for the evolution 

 of the Flagellata and subsequently also of other types of 

 Protozoa. Since about the time of E. A. Minchin (1912, cf. 

 Hall), however, the Flagellata have usually been given the 

 first place because they have been considered as a form that 

 had developed from the Phytoflagellata. Pascher has later 

 especially brought forward important arguments in favour 

 of this new interpretation. This, however, did not mean that 

 this difficult problem has been definitely solved. On the one 

 hand there appeared Sachwatkin (1956) as an assiduous 

 propagator of the older interpretation which beHeves in a 

 priority of Rhizopoda and of amoebae. On the other hand 

 Grasse (1948), an excellent and experienced researcher in 

 Protozoa, has recently suggested that the two large groups of 

 Protozoa should become united into a new group which he 

 called Rhizoflagellata. These should represent a large uni- 

 form central group which had served as a starting point for 

 the evolution of all the other groups of Protozoa. The main 

 argument Sachwatkin brings forward to support his theory 

 of the priority of the Rhizopoda is— besides the unpolarized 

 character of these animals and a supposedly primary absence 

 of flagella which Sachwatkin derives from the actinopodia 

 of the Heliozoa— above all their primary heterotrophic type of 

 feeding. He brings this fact in connection with Oparin's 

 theory of the origin of organisms. The possibility cannot be 

 24* 



