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University of California Publications in Zoologij [Vol. 16 



uncertain, but the fact that the centriole does not move out to become 

 the blepharoplast (Minehin, 1912) seems assured. It may, however, 

 arise by a division of that body, a supposition that would explain its 

 function as the division center for the cell, and also the occurrence of 

 another division center in the nucleus itself, both of which conditions 

 are common among the flagellates. This would, in reality, provide for 

 two division centers in the cell, one of which may remain iu the nucleus 

 and the other functions as the blepharoplast. This condition is found 

 in Polymustix bufonis. Both division centers may also be contained 



Figs. 11-14. Ndgleria gruberi (Schanlinger), after Wilson (1916), X 2080. 

 Fig. 11. Individual at the beginning of formation of the flagella: granule 

 appearing at the side of the karyosome. Fig. 12. A further development of 

 the blepharoplast which has reached the periphery of the nucleus. Fig. 13. 

 Further development of the same. Fig. 14. Flagellate form with two flagella 

 and blepharoplast connected with the karyosome of the nucleus by a rhizoplast. 



in one structure, as in the blepharoplast of Trichomonas (Kofoid and 

 Swezy, 1915a, b), where there may be a temporary separation of the 

 blepharoplast into the definitive centrosome and the basal granule. 



The claim is not made here that the amoeba is a more primitive 

 form than the flagellates. It is possible, however, that this change to 

 a flagellate stage occurs only in the more primitive amoebas wliich may 

 be on that account more unstable in their organization. Being nearly 

 allied to the original monad from which both the Rhizopoda and the 

 Plagellata may have sprung, the characteristics of both lines may thus 

 appear in the individuals of one line, owing to adverse, or at least to 

 some slight changes, in their environment. The tendency of the sim- 

 pler flagellates to become amoeboid under like conditions, and also 

 preceding degeneration, is probably another manifestation of this 

 primitive relationship. 



