1919] Kofoid-Swrsy: Str(blomastix strix 13 



Multiple fission stages which we have seen provide for eight 

 sehizonts when the Plasmodium parts by plasmotomy into its con- 

 stituent zooids. From irregularities in the number of nuclei in prep- 

 arations in which multiple fission is common, it seems probable that 

 plasmotomy is an irregular dropping off of individuals or groups of 

 individuals from the common mass as in Trichomonas. We have no 

 evidence as to the presence of a centrosome during multiple fission 

 and none as to the origin of the new blepharoplast-flagella complexes 

 of the daughter sehizonts. 



ADAPTATIONS 



Although seemingly simple in structure Streblomastix presents a 

 series of structural adaptations which in the light of its parasitic mode 

 of life become significant of intimate correlations with the conditions 

 under which it exists and its habits. The entire loss of the eytostome 

 is associated with feeding by osmosis and results in the disappearance 

 of the bilateral asymmetry characteristic of polymastigotes such as 

 Trichomonas. The absence of large food particles makes possible the 

 elimination or reduction of cyclosis of the endoplasm and facilitates 

 the change of form to a long and relatively verj^ narrow spindle 

 within which such movement would be impeded. The spiral course 

 of the mj'onemes or spiral striae provides a most effective form of 

 mechanism for an energetic thriist of the holdfast blepharoplast 

 again.st or into the cells of the host. It is also a form of contraction 

 which would disturb but slightly the closely packed grouping of the 

 parasites. The spirally fluted surface combined with the action of 

 the posteriorly directed flagella would give rise to vortex currents 

 of the circumambient digestive fluids and thus provide the circulation 

 essential to the metabolism of the parasite while at the same time 

 permitting their segregation apart from the other organisms of the 

 digestive tract of the host. The contractile extrusible rhizoplast- 

 blepharoplast complex with its blob of cytoplasm affords an efficient 

 structural holdfast. The elongation of the nucleus provides a spa- 

 tially advantageous grouping for the nueleo-cytoplasmic interchanges 

 in the absence of marked cyclosis. 



The neuromotor apparatus is so arranged as to give well distributed 

 contact with the surrounding medium by means of flagella and striae 

 and with the host by means of the blepharoplast-rhizoplast, while this 

 in turn is connected with the nucleus, thus establishing the structural 

 essentials for efficient coordination of functions. 



