PROTOPLASM 



45 



layer of the ectoplast (the " pellicle " of Infusoria and some Amoeba?) ; (c) a 

 secreted layer ("cell membrane") rather than a modification of the 

 ectoplast. In certain cases definite actively protective organs, the tri- 

 chocysts, are differentiated in the ectoplasm. 



Among the ectoplasmic structures with a motor function the simplest 

 are the pseudopodia; in the larger ones there is a core of endoplasm (Fig. 

 9), but the more delicate "filose" ones consist entirely of ectoplasm (Fig. 

 10). The flagellum of Euglena was reported by Biitschli to have an elas- 



FIG. 10. Gromia oviformis, 

 showing filose-reticulate pseu- 

 dopodia composed of ectoplasm. 



(From Minchin, after Schultze.) 



FIG. 11. 



A, flagellum of Euglena, showing endoplasmic core 

 and ectoplasmic sheath. (After Biitschli.) B, Trypano- 

 soma tincce, with undulating membrane. (After Min- 

 chin.) C, Trypanosoma percce, showing myonemes. (After 

 Minchin.) D, flagellum of Euglena. (After Bellinger.) 



tic endoplasmic core with a contractile ectoplasmic sheath (Fig. 11, A), 

 but the later figure of Bellinger (1909) represents it as composed of four 

 twisted filaments ending within the animal as a system of branching 

 rootlets (Fig. 11, D). Cilia, which are short and numerous and show 

 rythmic pulsation; cirri, which are formed of tufts of cilia; membranellce, 

 representing fused rows of cilia; and undulating membranes, which are 

 sheet-like extensions of the ectoplasm (Fig. 11, B), are all essentially 

 ectoplasmic organs. A further motor differentiation is seen in the 

 minute contractile fibrils known as myonem.es, which are analogous to a 



