240 Prof. H. Fol 07i the Family Tintinnodea. 



This arrangement once understood, it is easy to ascertain 

 that the large motor cilia are implanted 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. 

 In other words, all the cilia, whatever they may be, which 

 garnish the disk are implanted in accordance with about 

 twenty parallel spiral lines. Each row commences tangen- 

 tially to the margin of the disk by a certain number of motor 

 cilia, then curves towards the centre, bearing thick short cilia, 

 gradually diminishing from the periphery towards the centre. 



The entrance to the mouth meets the surface of the disk 

 obliquely, the pharynx being directed towards the left, at the 

 same time gradually contracting (figs. 2 and 3). By looking 

 at the animal in profile (fig. 2) it is easy to see that the 

 pharynx is lodged in a pouch-like lateral projection of the 

 body of the Infusorian. This projection is more strongly 

 marked in certain species, and becomes very striking in 

 meagre individuals when placed exactly in profile (fig. 2). 

 We then see that a certain number of the rows of cilia of the 

 disk (those, no doubt, which start from the margin of the 

 peristome nearest to the mouth) 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 which I have just described in 

 detail. All the rest of the surface of the body of the species 

 that I have observed was smooth ; at least it is hardly pro- 

 bable that cilia, however fine they might be, could have 

 escaped my observation had they actually existed. 



The description that I have just given may seem long. 

 This is because the difficulty of observation is extreme, be- 

 cause the eye must be aided by reasoning, in order to succeed 

 in understanding an arrangement so complex and so novel in 

 science, and because I determined to follow in my exposition 

 the same order as in my researches, so as to facilitate the 

 verification of my results. 



Clapar^de and Lachmann (VII. p. 192) indicate as the 

 general character of the Tintinnodea that these animals are 

 ciliated on their whole periphery, and that the peristome bears 

 vigorous cirri, forming several concentric rows. We have 

 just seen that the general ciliary covering is deficient in many 

 species, and that the cilia of the peristome present an arrange- 

 ment very different from that indicated by the above authors. 



