. Protozoo?logy. Protozoa; Protozoa, Pathogenic. CLASSIFICATION OF THE MASTIGOPHORA 51 pointed and are used by the animal as piercing needles for pene- trating the membranes of the victims that are caught for food. The more than superficial resemblance of these suctoria to the heliozoa gives a clue to the possible evolution of the infusoria from sarcodina. We have seen that in forms like myriophrys, cilia and pseudopodia are ecpially distributed around the body. We have also seen that the central axis of such pseudopodia and flagella are of the same type, and are probably homologous structures
. Protozoo?logy. Protozoa; Protozoa, Pathogenic. CLASSIFICATION OF THE MASTIGOPHORA 51 pointed and are used by the animal as piercing needles for pene- trating the membranes of the victims that are caught for food. The more than superficial resemblance of these suctoria to the heliozoa gives a clue to the possible evolution of the infusoria from sarcodina. We have seen that in forms like myriophrys, cilia and pseudopodia are ecpially distributed around the body. We have also seen that the central axis of such pseudopodia and flagella are of the same type, and are probably homologous structures; furthermore, we have seen that in actinobolus, projectile tentacles armed with trichocysts can be thrown out at any point on the periphery. These facts indicate the possibility of a common ancestry of the infusoria Fig. 19 11 m. a Cilia and myonemes of infusoria: a, h and e after Johnson; c, d, f and g after Biitschli. The surface view of Stentor ceruleus (c, e) shows rows of cilia inserted on the borders of canal-like markings, each of which contains a myoneme id). These are more clearly shown in the optical section (f). In Holophyra discolor {g) the canals and myoneraes are inserted deeper in the cortical plasm, a, the membrane of Stentor ceruleus under pressure. from a heliozoon-like ancestral race, represented in present-day forms by types like myriophrys, hypocoma, ileonema, and mesodinium, which have both tentacles and cilia. From such an ancestral group the ciliata may have arisen by losing the tentacles and adapting the cilia to the various needs of the cell, while the suctoria may have arisen by loss of the cilia and development of the tentacles to meet all of the needs of the cell, the cilia appearing in the embryos of the suctoria as reminiscences of the earlier ciliated condition of the race. These motile organs of the protozoa, with the exception of the flagella, are products of the cortical protoplasm, the flagella retaining. Please note that these images are ex
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