396 THE PROTOZOA 



lated stages in the life-history. In the first -place, the micro- 

 gametes are very often flagellated, as has been stated frequently 

 in the two foregoing chapters. In the second place, the youngest 

 stages in the development the merozoites or sporozoites exhibit 

 structural features which are either those of a flagellate swarm- 

 spore (Hartmann, 675 ; Schaudinn, 132), or can readily be derived 

 from a flagellula in which the flagellar apparatus has become rudi- 

 mentary, as in the sporozoites of gregarines, where the rostrum may 

 be interpreted, with a high degree of probability, as representing 

 a rudimentary flagellum. The existence of flagellated stages of 

 the kinds mentioned in the development of the Telosporidia is by 

 no means, however, a cogent argument for a flagellate ancestry for 

 the group, since quite typical Sarcodina of all orders exhibit flagel- 

 late swarm-spores and gametes. It may be urged that in the case 

 of these types of Sarcodina, also, the existence of flagellate stages 

 indicates a flagellate ancestry ; but such an argument merely 

 evades the question at issue, which is not whether the Telosporidia 

 are derived from Flagellata indirectly through Sarcodine ancestors, 

 but whether or not they are descended directly from ancestors 

 that were typical Flagellata. The existence of flagellated swarm- 

 spores and of gametes representing a modification of such swarm- 

 spores is not sufficient of itself to prove a flagellate ancestry fen: the 

 Telosporidia. 



Far more cogent arguments for the flagellate affinities of the 

 Telosporidia may be drawn from the characters of the adult forms, 

 especially from the gregarine-type of body, elongated and ver- 

 micular in character, and perfectly definite and constant in form, 

 which occurs in every group of the Telosporidia at one point or 

 another in the life-history. Such a type of body can be readily 

 derived, as Butschli (2) pointed out, from an organism similar to 

 Astasia or Euglena, in which the flagellar apparatus has been lost, 

 and all special organs of nutrition, whether holozoic or holophytic, 

 have disappeared in- relation with the parasitic mode of life. On 

 the other hand, the gregarine-type of body cannot be derived from 

 the adult forms of the Sarcodina, which are typically amoeboid, 

 and without any definite body-form other than that imposed by 

 the physical nature of their body-substance. 



We may therefore consider the ancestral form of the Telosporidia 

 to have been a flagellate organism with an elongated form of body, 

 with a definite form, owing to the presence of a cuticle of a certain 

 degree of thickness and toughness, and with a flagellar apparatus 

 at the anterior end. Such a form would have been not unlike the 

 leptomonads now found commonly as parasites of insect-guts ; 

 but there is no reason to suppose the ancestral form to have had 

 a kinetonucleus and the third type of flagellar insertion. Such a 



