GENUS PETALOTRICHA. 629 



only a few lines of cilia that actually reach the entrance of the mouth, and these are 

 precisely the shortest ones. The others stop so as to leave the central part of the 

 disc naked. All the rows just mentioned are formed of thick, short, slightly recurved 

 cilia, scarcely attenuated at their free extremity, and only beating for moments. 

 Their length decreases regularly from the margin of the peristome, which bears the 

 thickest and longest, to the inner extremity of the line, which is formed of much 

 shorter and more slender cilia. On returning to the motor cilia to ascertain what 

 relation they bear to the cilia of the disc, it is noticeable, in the first instance, that 

 the margin of the peristome, viewed from its upper surface (Woodcut, Fig. 2), is not 

 simply rounded, but denticulate. The teeth resemble those of an ordinary saw, and 

 are all turned in the same direction, and this direction is precisely that towards 

 which the rows of short thick cilia deviate. Each of the rows indeed corresponds to 

 one of the denticulations in such a manner that it terminates at the base of the 

 longer side of the denticulation, or that which forms a tangent to the margin of the 

 disc. The arrangement once understood, it is easy to ascertain that the large motor 

 cilia are upon the longer margin of each denticulation, hence they do not form a 

 continuous circular or spiral line, but a broken line, the segments of which are only 

 simple continuations of the rows of short cilia." 



" The entrance to the mouth, or Fig. 2, meets the surface of the disc obliquely, 

 the pharynx being directed towards the left, at the same time gradually contracting. 

 By looking at the animal in profile (Woodcut, Fig. i) it is easy to see that the 

 pharynx, ph, is lodged in a pouch-like lateral projection of the body of the Infusor. 

 A certain number of the rows of cilia of the disc descend into the pharynx and there 

 form a series of nearly straight parallel lines composed of extremely fine cilia. The 

 actual margin of the mouth is furnished with tolerably stout and long cilia which 

 beat energetically ; but I have not succeeded in ascertaining precisely what relation 

 may exist between these cilia and those just described in detail. All the rest of the 

 body was smooth ; at least, it is hardly probable that cilia, however fine they might be, 

 could have escaped my observation had they actually existed." 



The position of either the endoplast or contractile vesicle was not determined by 

 Professor Fol. Several instances of conjugation were observed in which two 

 animalcules were intimately united to each other by their peristomal margins. 



Petalotricha spiralis, Fol. WOODCUT, p. 628, FIG. 3. 



Lorica greatly elongated, pointed, drawn out ; the posterior third nearly 

 cylindrical, very narrow, terminated by an acute point ; the anterior two- 

 thirds having the form of an elongated cone, slightly inflated ; near the orifice 

 a thickening in the form of a cushion projecting outwardly ; substance of 

 lorica composing two very distinct layers, presenting at the surface some 

 faintly marked and somewhat irregular striae, generally parallel, disposed 

 obliquely to the axis of the test, and describing very elongate dextrogyrous 

 spirals; small points arranged in spiral lines parallel to the striae, and 

 alternating with them ; the cushion that surrounds the orifice formed 

 solely by the outer layer ; animalcules short, peduncle much elongated, 

 attached at a considerable distance from the apex of the test, or even pre- 

 senting two points of attachment ; curved lines of peristomal cilia number- 

 ing about twenty ; body apparently smooth. Length of lorica 1-62". 



HAB. Salt water : Villefranche. 



Described by Professor Fol under the title of Tintinnus spiralis. 



