MORPHOLOGY 61 



(p. 38). 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 membranous 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 processes, and thus the capsule is to be con- 

 sidered as a protective organella. The endoskeletal structures of 

 Radiolaria vary in chemical composition and forms, and are ar- 

 ranged with a remarkable regularity (pp. 371-376). 



In some of the astomous 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 

 pecuhar organella, furcula, observed by Lynch in Lechriopyla 

 (p. 536) is said to be concerned with either the neuromotor system 

 or protection. The members of the family Ophryoscolecidae, 

 which are common commensals of the stomach of ruminants, 

 have conspicuous endoskeletal plates which arise in the oral 

 region and extend posteriorly. Dogiel (1923) believed that the 

 skeletal plates of Cycloposthium and Ophryoscolecidae are made 

 up of hemicellulose, "ophryoscolecin," which was also observed 

 by Strelkow (1929). MacLennan found that the skeletal plates of 

 Polyplastron multivesiculatuni were composed of small, roughly 

 prismatic blocks of glycogen, each possessing a central granule. 



In certain Polymastigina and Hypermastigina, there occurs a 

 flexible structure known as the axostyle, which varies from a 

 filamentous structure as in several Trichomonas, to a very con- 

 spicuous rod-like structure occurring in Parajoenia, Giganto- 

 monas, 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 which have connections with the 

 flagella as seen in Polymonadina and certain Hypermastigina 

 such as Lophomonas. Kirby showed that in Trichomonas tennop- 

 sidis, the axostyle and the granules occurring in it, are of glycog- 

 enous substance. 



In trichomonad flagellates there is often present along the at- 

 tachment of the undulating membrane a rod-like structure which 

 has been known as costa (Kunstler) and which, according to 



