6 Mr. R. Vallentin on the 



branous walls and narrowing towards its distal extremity, 

 where it apparently opens into the retracted vestibule. This 

 tube corresponds in its relations with the so-called " taster " of 

 Dr. Hudson, and is, in my opinion, identical with it. On 

 reference to PI. II. fig. 14 the opening of this duct into the 

 vestibule can be seen. Fig. 13 shows the proximal extremity 

 of the duct with the secretion therein and its connexion with the 

 apex of the so-called " brain." The suggestion I offer is this : 

 the organ is of a salivary nature, the " tongue " or " taster " 

 being a duct, its use being that as each particle of food is 

 passed into the vestibule a minute portion of this secretion 

 passes with it. This view seems all the more probable when 

 we consider that salivary glands, which are present in the 

 majority of the Rotifera, are absent in this species. As- 

 suming this to be the case, is there any other structure to 

 which one can point as being nervous ? This, I think, can 

 be answered in the affirmative. No observer can have failed 

 to notice in the living animal the large, oval, nucleated cells 

 placed close to the cuticle on either side of the collar. Dr. 

 Hudson {loc. cit.) says, " oval nucleated cells are also easily 

 seen in the wall of the coronal cup when the animal is viewed 

 from either side." Sections taken in a plane parallel to 

 the long axis of the animal show these to resemble in a 

 marked degree unipolar ganglion-cells ; the single process 

 given off from each cell running anteriorly and terminating in 

 the plumes or arms (PL II. fig. 1). This appears to receive 

 further confirmation on the examination of Melicerta ringens. 

 When this Rotiferon is protruding from its tube, the two paired 

 antennas placed ventrally, the paired recurved hooks and the 

 rudimentary third antenna placed between them protect it 

 dorsally, and so it is guarded on all sides. Sections show 

 each of these to be furnished with a nerve-fibre, clearly showing 

 their sensory nature. In Stephanoceros, however, we find 

 the plumes or arms performing two functions : they act as 

 tactile organs, and, being furnished with setse, as food-collectors 

 for the animal. 



Eyes. — The remarks I have to make regarding these struc- 

 tures do not agree with those made by previous investigators. 

 Dr. Hudson (loc. cit.) says, " The eyes lie on either side of 

 the nervous ganglion ; they may be seen by a dark field 

 illumination." Mr. Cubitt (loc. cit.) gives the most exhaustive 

 account. He says, " Their true character is difficult to deter- 

 mine ; they resemble in a marked degree the eyes of Verte- 

 brates, consisting of a globe, sending off posteriorly a fibre to 

 the brain, and possessing anteriorly a pigment-spot, which, 

 while favouring the form of a compound type, contains within 



