GOSSE, ON DYSTERIA. 139 



fission, and with cilia as locomotive organs, is a combination 

 of characters found only in the Infusoria."^ 



Now the presence of a contractile vesicle, and of locomo- 

 tive cilia, are quite as characteristic of the Rotifera as of 

 the Infusoria. The absence of an alimentary canal is, I 

 think, not proved : it seemed to me that the animal possessed 

 a defined digestive cavity, though very ample. In Sacculus, 

 — an indubitable Rotiferon, which carries its large eggs in 

 the manner of a Brachionus, — the alimentary canal, without 

 apparent distinction of stomach and intestine, is so large 

 that it occupies fully five sixths of the whole volume of the 

 lorica ; and though it is invariably found filled with a green 

 alga, on which the animal feeds, the walls of the digestive 

 cavity are not better defined than in Dijsteria. There re- 

 mains then only the fact of increase by transverse fission. 

 This, I confess, is a strong point, if well established. But 

 it does not seem certain, from Mr. Huxley's words, whether 

 he witnessed the progress of constriction, from an early 

 stage, until two perfect animals were formed out of one, or 

 only saw an individual so strongly constricted that the re- 

 sult seemed legitimately inferible. If the latter was the 

 case, is it not just possible that it was an example, not of 

 spontaneous fission, but of malformation, instances of which 

 are frequent among the highest animals ? It is highly Avorthy 

 of note that the nucleus, so characteristic of the Infusoria, 

 was not found, even under careful search with acetic acid. 



The presence, position, and movements of the foot, hinged, 

 as it is, upon a tubercle, and the form of the principal organs 

 of manducation, seem to me to determine the place of I>ys- 

 teria within the class Rotifera ; while, at the same time, 

 the lack of internal motion, the apparent want of distinct 

 muscle-bands, the great extent of the vibratory cilia, and the 

 absence of a rotatory arrangement, show that it occupies 

 one of the vanishing points of the class. 



If this allocation be admissible, it is interesting to inquire, 

 what are the recognised forms among the Rotifera to 

 which this animal makes the most obvious approaches. The 

 foUoAving points of relationship occur to me : 



1. The oval form and bivalve character of the lorica sug- 

 gest the Coluridce, with which the creature associates ; but 

 they have the valves separate only on the ventral edge. 



3. The Salpinad(B, on the other hand, have the lorical 

 plates separate down the dorsal edge, but soldered together 

 ventrally, the foot playing in a fissure. 



* Loc. cit., p. 82, 



