MORPHOLOGY 61 



system includes three structures: namely, the peculiarly ridged 

 pellicle; trichocysts which have no fibrillar connections among 

 them or with fibrils, hence not conductile; and the subpellicular sys- 

 tem, the last of which is that part of the neuromotor system that 

 concerns with the body cilia, ten Kate (1927) suggested that senso- 

 motor apparatus is a better term than the neuromotor apparatus. 



Protective or supportive organellae 



The external structures as found among various Protozoa which 

 serve for body protection, have already been considered (p. 39). 

 Here certain internal structures will be discussed. The greater part 

 of the shell of Foraminifera is to be looked upon as endoskeleton 

 and thus supportive in function. In Radiolaria, there is a mem- 

 branous structure, the central capsule, which divides the body into 

 a central region and a peripheral zone. The intracapsular portion 

 contains the nucleus or nuclei, and is the seat of reproductive proc- 

 esses, and thus the capsule is to be considered as a protective or- 

 ganella. The endoskeletal structures of Radiolaria vary in chemical 

 composition and forms, and are arranged with a remarkable regular- 

 ity (pp. 418-425). 



In some of the astomatous euciliates, there are certain structures 

 which seem to serve for attaching the body to the host's organ, but 

 which seem to be supportive to a certain extent also. The peculiar 

 organella /wrcwZa, observed by Lynch in Lechriopyla (p. 597) is said 

 to be concerned with either the neuromotor system or protection. 

 The members of the family Ophryoscolecidae (p. 654), which are 

 common commensals in the stomach of ruminants, have conspicuous 

 endoskeletal plates which arise in the oral region and extend posteri- 

 orly. Dogiel (1923) believed that the skeletal plates of Cycloposthium 

 and Ophryoscolecidae are made up of hemicellulose, "ophryoscole- 

 cin," which was also observed by Strelkow (1929). MacLennan 

 found that the skeletal plates of Polyplastron multivesiculatum were 

 composed of small, roughly prismatic blocks of paraglycogen, each 

 possessing a central granule. 



In certain Polymastigina and Hypermastigina, there occurs a 

 flexible structure known as the axostyle, which varies from a fila- 

 mentous structure as in several Trichomonas, to a very conspicuous 

 rod-like structure occurring in Parajoenia, Gigantomonas, etc. The 

 anterior end of the axostyle is very close to the anterior tip of the 

 body, and it extends lengthwise through the cytoplasm, ending near 

 the posterior end or extending beyond the body surface. In other 

 cases, the axostyle is replaced by a bundle of axostylar filaments 



