MORPHOLOGY 39 



The ectoplasm is the cortical zone which is hyaline and homogene- 

 ous. In the Ciliophora, it is a permanent and distinct part of the body 

 and contains several organellae; in the Sarcodina and the Sporozoa, 

 it is more or less a temporarily differentiated zone and hence varies 

 greatly at different times and, in the Mastigophora, it seems to be 

 more or less permanent. The endoplasm is more voluminous and 

 fluid. It is granulated or alveolated and contains various organellae. 

 While the alveolated cytoplasm is normal in forms such as the 

 members of Heliozoa and Radiolaria, in other cases the alveolation 

 of normally granulated or vacuolated cytoplasm indicates invariably 

 the degeneration of the protozoan body. In Amoeba and other 

 Sarcodina, the "hyaline cap" and "layer" (Mast) make up the 

 ectoplasm, and the "plasmasol" and "plamagel" (Mast) compose 

 the endoplasm (Fig. 44). 



In numerous Sarcodina and certain Mastigophora, the body 

 surface is naked and not protected by any form-giving organella. 

 According to the observations by Kite, Rowland, and others, the 

 surface layer is not only elastic, but solid, and therefore the name 

 plasma-membrane may be applied to it. Such forms are capable of 

 undergoing amoeboid movement by formation of pseudopodia and 

 by continuous change of form due to the movement of the cytoplasm 

 which is more fluid. However, the majority of Protozoa possess a 

 characteristic and constant body form due to the development of a 

 special envelope, the pellicle. In Amoeba striata and A. verrucosa, 

 there is a distinct pellicle. The same is true with some flagellates, 

 such as certain species of Euglena, Peranema, and Astasia, in which 

 it is elastic and expansible so that the organisms show a great deal 

 of plasticity. 



The pellicle of a ciliate is much thicker and more definite, and 

 often variously ridged or sculptured. In many, linear furrows and 

 ridges run longitudinally, obliquely, or spirally; and, in others, the 

 ridges are combined with hexagonal or rectangular depressed areas. 

 Still in others, such as Coleps, elevated platelets are arranged paral- 

 lel to the longitudinal axis of the bodJ^ In certain peritrichous 

 ciliates, such as Vorticella monilata, Carchesiiim granulatum, etc., 

 the pellicle may possess nodular thickenings arranged in more or less 

 parallel rows at right angles to the body axis. 



While the pellicle always covers the protozoan body closely, 

 there are other kinds of protective envelopes produced by Protozoa 

 which may cover the body rather loosely. These are the shell, test, 

 lorica or envelope. The shell of various Phytomastigina is usually 

 made up of cellulose, a carbohydrate, which is widely distributed 



