276 Prof. H. J. Clark 07i the Animal Nature 



tance posterior to the mouth {m), and distinctly disconnected 

 from it, as has been already noticed. When not in motion, 

 which seldom occurs, the brush lies along the median furrow 

 (m/), which trends from the mouth to the posterior end of the 

 animal ; and in this position it projects for nearly half its length 

 beyond the body. Its most ostensible use would seem to be 

 that of a sort of rudder when the creature is swimming, and as 

 a means of attachment when not progressing. The body may 

 be seen gyrating and at the same time revolving on its longi- 

 tudinal axis, for long periods, around a point to which the 

 pseudo-flagellum is attached, and upon which it turns like 

 a pivot. Most frequently, during this act, a part of the 

 brush separates from the rest, and performs the office of an 

 extra propeller. When the animal is darting and spinning 

 through the water, this appendage projects obliquely from its 

 point of attachment (as in fig. 1), and always following, with 

 the narrower end of the body, in the rear, it seems pretty evi- 

 dently to be the main agent in the various and sudden tackings 

 to which this Infusorian is addicted, and also the axis upon 

 which the body revolves ; at least the latter whirls, repeatedly 

 changing as quick as thought from right to left, or vice versa, 

 upon an imaginary axis, which is oblique to its greatest length, 

 and which exactly corresponds to the trend of the flagelliform 

 appendage when operating in this capacity. Under these con- 

 ditions the animal shoots along with a compound motion, which 

 might be described as wabbling, or like the action of an excen- 

 tric wheel. Apparently in confirmation of this view, the annular 

 obliquely transvei-se anterior {af) and posterior {pf) furrows 

 trend almost exactly at right angles to this imaginary axis. 

 These two furrows seem, at first sight, to be bands of vibrating 

 cilia ; and in fact it is in the line of their trend that these cilia 

 are most readily detected, simply because they are rather more 

 crowded along their edges than elsewhere ; but an attentive ex- 

 amination reveals their presence all over the body, posterior to 

 the anterior transverse furrow. Between the two furrows {i. e. 

 from af to pf) they are longer than at the narrower end of 

 the body, and at both points they have a pretty uniform length, 

 moderate extension, and are very delicate, so as not to be easily 

 observed when the body is in motion. At the anterior trans- 

 verse furrow they appear to be a little longer than elsewhere, 

 and, acting more or less in concert, they have the semblance of 

 a wreath disposed along the edge of the low skullcap-hke cover- 

 ing (pc) of the anterior end. 



The Cuirass (pc). — It is pretty evident that in the species be- 

 fore us this is a mere dermal specialization, without any trace 

 of indurated matter which would entitle it to the name of a 



