Emdence from Protozoans 57B 



origin of the organ. In otlicr words, the question is, are we 

 going to reject the positive evidence we actually have, in 

 the interest of a pure speculation? Even should further 

 study find that, contrary to Patton's obsei*vations, there is 

 a granule at the base of the flagellum of Herpetomonas 

 lygaei which gives rise to an axial core, the observation that 

 the achromatic substance of the cell participates in the 

 formation of the flagellum would not be set aside thereby. 



{(I) J'ario2is Organs of Sfylonychia and Paramecium 



In the chapter on the an;itomy of the protozoa we took 

 Stylonychia as an example of the high degree of specialization 

 and integration which the sensory-locomotor system may reach 

 in a one-celled animal. While the ontogeny of this genus has not 

 been studied as fully as is desirable^ yet the combined knowledge 

 we have of its structure and regeneration is sufficient to leave 

 no room for doubt that the ectoplasm and the outer strata of 

 endoplasm take an active part in producing the elaborate sensory 

 and motor organs. For example^ the basal fibers {h. f., figure 6) 

 are shown by Maier to be attached to the basal edge of the 

 membranellae and to run inward in the endoplasm, where they 

 gradually taper to very fine endings not connected with either 

 the macronucleus or micronuclei or granules of any kind. The 

 inference seems unescapable tliat ontegenetically at least they 

 arise in the ectoplasm and grow inward. Again, as to the ecto- 

 plasm itself, Maier points out that in some parts of the animal 

 this is laid off into definite areas, each one of which is deeply 

 cupped outwardly and bears a cilium with its basal granule at 

 its center. This disposition is specially clear in Paramecium 

 cauda-ium. To suppose that such a differentiation of the ecto- 

 plasm is due to the "influence" of the basal granule, the ectoplasm 

 itself being passively moulded, would be so gratuitous that 

 probably no biologist would be bold enough to make it definitely ; 

 yet exactly that assumjDtion would be necessary were "form- 

 determination" to be denied to everything but chromatin. 



Only one other developmental' point can be noticed in connec- 

 tion with Stylo7iy cilia, that concerning the production of the un- 

 dulating membrane {m h p., figure 6). That this organ be- 

 longs to the ectoplasm is generally recognized, and the considera- 



