PROTOZOA : INFUSORIA. 



71 



cium and Vorticella may be selected, the former being free, 

 whilst the latter is permanently fixed in its adult condition. 



Paramxcium (fig. 10, c) is a slipper-shaped animalcule, com- 

 posed externally of a structureless transparent pellicle — the 

 " cuticle " — which is lined by a layer of firm and consistent sar- 

 code, which is termed the " cortical layer," or the " parenchyma 



Fig. 10. — Morphology of Infusoria; ei Eptstylis, a stalked Infusorian ; bA single 

 calyx of the same greatly magnified, showing the ciliated disc which protrudes at 

 will, and the ciliated internal cavity into which the particles of food are received. 

 In the substance of the body are the contractile vesicle and smaller food-vacuoles. 

 c Diagrammatic representation of Faramcsciuftt, showing the funnel-shaped gullet, 

 the nucleus and nucleolus, food-vacuoles, and two contractile veisicies. d Aspidisca 

 iyiiceus ; e Fentiiejna glohuiosA, a flagellate Infusorian. 



of the body," this in turn passing into a central mass of softer 

 and more diffluent sarcode, known as the "chyme-mass," or 

 " abdominal cavity." The " cuticle " is covered with vibratile 

 cilia, and is perforated by the aperture of the mouth. The 

 mouth leads into a funnel-shaped gullet, which is not continued 

 into any distinct digestive sac, but is lost in the central "chyme- 

 mass." Within the " cortical layer " are the " nucleus " and 

 " nucleolus," and the " contractile vesicle " (or vesicles). The 

 nucleus is usually a solid band or rod-shaped body, having a 

 small spherical particle applied to its exterior, or immersed in 

 its substance. This latter is the so-called "nucleolus," which 

 must be carefully distinguished from the nucleolus of a cell, 

 which occurs in the interior of the nucleus. The contractile 

 vesicles are clear spaces, which contract and dilate at intervals, 

 and occasionally exhibit radiating canals passing^ into the sur- 

 rounding sarcode. Ordinarily one contractile vesicle is present, 

 or at most two, but in some cases there may be several. It 

 has also been maintained that the contractile vesicles com- 

 municate with the exterior of the body, .but proofs are wanting 

 on this point. Whether this should ultimately be established 



