GENUS PRORODON. 493 



elliptical, of small dimensions ; contractile vesicle single, postero-terminal, 

 communicating at the time of systole with three or four spherical lateral 

 sinuses ; numerous trichocysts enclosed in the cortex of the anterior half of 

 the body, none in the posterior one. Length 1-250". Hab. — Pond water. 



Prorodon edentatus, C. & L. Pl. XXVI. Fig. 43. 



Body elongate-ellipsoidal, cylindrical, nearly three times as long as 

 broad, transparent, surface of cuticle longitudinally striate, striae separated 

 considerably from one another ; oral aperture terminal, slightly eccentric ; 

 pharyngeal armature consisting of a simple, conical, corneous tube developed 

 backwards to the centre of the body and gradually diminishing in size as it 

 approaches the posterior end ; endoplast oval, elongate ; contractile vesicle 

 single, spherical, postero-terminal ; no trichocysts ; cilia of the posterior 

 extremity longer than those of the general surface, produced in a tuft- 

 like manner. Length of body 1-250". Hab. — Pond water. 



Prorodon marinus, C. & L. 



Body elongate, cylindrical, from two to two and a half times as long as 

 broad, the cuticular surface not longitudinally striate ; oral aperture exactly 

 terminal ; pharyngeal tube simple, edentulate, very small and short ; con- 

 tractile vesicle postero-terminal; endoplast ovate; colour transparent, 

 enclosing numerous dark, refringent granules. Length of body 1-250". 



Hab. — Salt water : Norwegian coast (C. & L.). 



Prorodon margaritifer, C. & L. Pl. XXVI. Fig. 44. 

 Body elongate-elliptical, subcylindrical, three times as long as broad, 

 slightly widest anteriorly ; cuticular surface finely and closely striate longi- 

 tudinally ; oral aperture subterminal ; pharyngeal tube large, consisting of 

 numerous, short, rod-like teeth ; contractile vesicles very numerous, com- 

 paratively small and spherical, distributed throughout the substance of the 

 cortical layer ; no trichocysts ; endoplast double, consisting of two obliquely 

 converging elliptical bodies, separated from one another at the nearest point 

 of convergence by a smaller spherical body which apparently represents 

 the nucleolus or endoplastule ; colour of the general substance of the body 

 clear brown, contents of the contractile vesicles pinkish. Length 1-75." 

 Habitat unrecorded. 



In the number of its contractile vesicles this species stands almost alone 

 among those representatives of the class Infusoria with which we are as yet 

 familiar. The figure here reproduced from Claparede and Lachmann's treatise,* 

 shows over forty of these vesicles on that side only of the animalcule which is 

 exposed to view, so that very few short of one hundred may be accepted as 

 the total number of these structures contained within the cortical layer of a 

 single zooid. These vesicles do not appear to have any communication with 

 one another, but expand and contract independently. A closely similar but less 

 numerical development of the contractile-vesicular system has recently been 

 found by the author to obtain in Trachdius oviim. Claparede and Lachmann 



* 'Etudes sur les Infusoires,' 1858. 



