LACINULARIA SOCIALIS 1 33, 



Now these thickenings are especially obvious in two localities — 

 1st, in the prolongation of the body below the visceral cavity;^ and 

 2ndly, in the trochal disc. 



Of the former thickenings, the four uppermost are promoted by 

 Professor Ehrenberg to be testes, for no other reason, apparently, 

 than that, having missed the true water-vascular system with its bands, 

 he knew not where else to find what he calls a male organ. 



Again, the thickenings (figs. 2, 3 r) in the trochal disc are mostly 

 towards its lower surface and at its inferior margin ; they are generally 

 four or five on each side, and are connected by branched filaments 

 with that body on each side of the pharyngeal mass in which the band 

 of the water-vascular system terminates. 



According to Professor Ehrenberg these are all ganglia, and the 

 two yellowish bilobed or cordate bodies on each side of the pharynx 

 are " comparable to a brain " ! 



Nei'vous System and Organs of Senser — On the oral side of the 

 neck of the animal, or rather upon the under surface of the trochal disc, 

 just where it joins the neck, and therefore behind and below the mouth, 

 there is a small hemispherical cavity (fig. 4 0) (about I-I400th of an 



' Leydig (loc. cit. pp. 467-8) regards the central vacuolar mass at the root of the tail as 

 a peculiar gland, from which he says a duct runs downwards to terminate at the extremity of 

 the tail. The purpose of this organ is to secrete the gelatinous envelope. I must confess 

 that I saw no grounds for this interpretation. The extremity of the tail always seemed to 

 me to present a ciliated hemispherical cavity, closed above. 



- Leydig {loc. cit. p. 457 et seq.) criticises at length, and altogether repudiates, the 

 mythical nerves and ganglions which Professor Ehrenberg has ascribed to Laciniilaria. 

 He does not appear to have seen either the ciliated cavity, or the body which I still 

 venture to think is the only true ganglion ; but describes a very peculiar nervous system, 

 consisting of — 



1. A ganglion behind the pharynx, composed of four bipolar cells, with their processes. 



2. A ganglion at the beginning of the caudal prolongation, similarly composed of four 

 larger ganglionic cells and their processes. 



The latter cells are what I have described as vacuolar thickenings. I could find no 

 difference whatever between them and the thickenings in the disc, which Leydig allows to 

 be mere thickenings. 



The former were not observed by me. I have not been able to repeat my investigations 

 upon this point, as I hope to do ; for the present I must offer as arguments against Leydig's 

 interpretation of the nature of the structures which he observed — 



1st. That the body which I describe as a ganglion is perfectly similar in appearance to the 

 mass on which the eye-spots of Brachionus are seated. 



2nd. That if such an arrangement of the nervous system as that which Leydig describes 

 exists, the Rotifera are very widely different from their congeners, and, indeed, from all 

 known animals. 



Leydig himself, however, says, — "That these cells, with their radiating processes, are 

 ganglion-globules and nerves, is a conclusion drawn simply from the histological constitution 

 of the parts, and from the impossibility of making anything else out of them, unless, 

 indeed, organs are to be named according to our mere will and pleasure." — Loc. cit. p. 459. 



