4 Mr. R. Vallentin on the 



collar close to the base of the arras. He notices, however, 

 that he has seen cases where the muscles run down direct 

 from the depressions between the lobes without uniting to 

 form pairs. My own opinion, after prolonged observation of 

 many specimens, is that there are really six pairs of muscles, 

 and that they are arranged in the following fashion. Each 

 pair runs up the foot, looking like a single muscle, and the 

 reason why never more than four (pairs) are visible in the 

 foot from any point of view is that there is always a pair on 

 each side of the animal (however viewed) which is there lost 

 to sight. At the junction of the foot and trunk each pair 

 begins to open a little, and by the time they have reached 

 the bottom of the coronal cup the constituents of each pair 

 diverge obviously from each other, and terminate usually at 

 the base of some one of the depressions between the lobes, 

 but in such a fashion that the constituents of the same pair 

 never end in the same depression." 



According to my observations their arrangement is as fol- 

 lows : — On reference to figs. 7-11 (PI. T.) four pairs of muscles 

 will be seen placed at equal distances from one another almost 

 immediately under the cuticle, the interspaces being occupied 

 by the mucous cells previously mentioned. Owing to the 

 tapering shape of the foot these muscles tend naturally to 

 converge towards the fixed extremity ; and so we find that in 

 this latter region they come into contact, the mucous cells 

 disappearing, the apex containing muscles only. At the junc- 

 tion of the foot with the body the muscles of each pair separate 

 a little, and as they run forwards keep close under the cuticle, 

 and never leave their own portion of the body. Anteriorly 

 they terminate in a sphincter- muscle placed in the collar at 

 the bases of the arms. So far as I have been able to gather 

 from previous writers it appears to me that sufficient import- 

 ance has not been attached to this muscle, styled by Mr. Gosse 

 " circular." On examining a living specimen in a healthy 

 condition, we find that when it retracts into the tube the 

 bases of the arms are brought together by the contraction of 

 this " circular " muscle, and the longitudinal muscles being 

 almost simultaneously brought into play, a rapid retreat of 

 the animal into its tube is the result. The presence of this 

 muscle is also evident when the animal issues forth again, 

 the arms being protruded as a bundle and then opened out, 

 the setae clothing them being immediately brought into play. 

 Nervous System. — Dr. Hudson (loo. cit.) is the only writer 

 who has hitherto seriously raised the question whether or not 

 that part of the Rotiferon which usually passes as the brain 

 is really a nervous structure. He says, " What is probably 



