CHAPTER V 



THE ORGANIZATION OF THE PROTOZOA (Continued) 

 DIFFERENTIATIONS OF THE ECTOPLASM AND ENDOPLASM 



A. Ectoplasmic Organs. 



THE various structures and organs produced from the ectoplasm 

 are best classified by the functions they subserve, under the headings 

 of protective, kinetic and locoinotor, excretory, and sensory 

 mechanisms. 



1. The protective function of the ectoplasm is often seen in 

 organisms in which no cuticle or envelope is present. It has been 

 observed, for instance, that the species of Myxosporidia that 

 inhabit the gall-bladders or urinary bladders of their hosts resist 

 the effects of the medium in which they live so long as their ecto- 

 plasm is intact, but succumb if it be injured. 



In most Protozoa other than those belonging to the class Sarco- 

 dina, however, a special protective envelope or cortex is present at 

 the surface of the body, and such forms are commonly said to be 

 corticate. A cuticle may be formed in various ways, distinguished 

 by the use of different terms. It may represent the entire ecto- 

 plasm, modified in its entirety to form an envelope, as in the peri- 

 plast of the Flagellata ; it may represent a transformation or modi- 

 fication of only the most superficial layer of the ectoplasm, as in 

 the pellicle of the Infusoria and of some amoebae for instance, 

 Amoeba verrucosa, the epicyte of the gregarines, etc. ; or it may arise 

 as a secreted layer deposited at the surface of the ectoplasm, and not 

 derived from a modification of the substance of the ectoplasm itself, 

 in which case it is termed a " cell- membrane." 



Whatever its mode of origin, the cuticle may be developed to a 

 very variable degree, from the thinnest possible membrane, some- 

 times very difficult to discover, to a thick and tough investment 

 which may be termed a " cuirass " or " lorica " (" Panzer "), when 

 it is formed by thickening of a pellicle ; or a " house " or " shell," 

 when it is a greatly thickened cell- membrane standing off from the 

 body. In many cases the cuticle undergoes local thickenings to 

 form spikes or hooks, which may serve as organs of attachment, 

 as in the epimerite of gregarines (Fig. 142). 



45 



