Classijication of Ciliate Infusoria. 231 



unique, although having some resemblance to that of tlie 

 Stentorina. There is no adoral zone with transverse rows of 

 cilia like that in Heterotricha and Hypotricha, as has recently 

 again been asserted by Delage et Herouard *. The arrange- 

 ment of the muscular elements in the ectoplasm, or myonems, 

 is quite different. The formation of a temporary posterior 

 girdle of cilia for locomotion in the most typical Peritricha, 

 and even the permanent one in some others, is a very distin- 

 guishing feature ; and a distinction of highest order is their 

 mode of fission in the longitudinal axis f <>i" by gemmation. 

 This character has been explained in various ways, and some 

 have tried to bring it in conformity with the transverse fission 

 in the other groups. Nevertheless it remains different, and 

 shows, combined with the other features noted above, that 

 this group is of quite another type or phylum, the more so if 

 we add the peculiar phenomena of conjugation. The re- 

 maining Ciliata differ from the Peritriciia in regard to these 

 characters, and they resemble one another in respect to the 

 most significant of them. 



In opposition to the Peritricha we may give to this second 

 group the name Pantotricha. Among the latter those forms 

 having a true adoral zone with a distinct beginning and end 

 at the mouth-entrance, and bearing transverse rows of single 

 cilia — that is, the Hypotricha and most of the Heterotricha — 

 evidently are of a common type^ and range in one group, 

 which 1 propose to name Zonotricha. True, the extreme 

 forms are very different, e. g. a Stentor on the one hand and 

 a Stylonychia or Eiijjlotes on the other; but it is well known 

 that both series, by gradual changes, in fact, run together, and 

 that there are forms which may be ranged with one or the 

 other. Many Peritricha are quite depressed, while there are 

 Oxytrichid^ nearly terete, showing little differentiation of 

 the dorsal and ventral faces, with fine and densely set cilia 

 over most of the body (^Strongylidium). And such forms as 

 StichospiraX make the distinction still more illusory. Tactile 

 hairs (or " dorsal cilia ") are wanting in some of the Oxy- 

 trichidaj, as well as in Euplotidee and Aspidiscidae. Longi- 

 tudinal differentiation in the ectoplasm of Urostyla &c. comes 

 very near the myonems in Peritricha. With the Zonotricha 

 range Ilalteria, probably also Stromhidium and Gyrocoris. 



* ' Traite de Zoologie Concrete : I. La Cellule et les Protozoah-es.' 

 Taris, 1896, p. 452. 



t it must be noted, however, that in all groups the du'ection of the 

 division is across that of the luyonems. 



X See the writer's article, ' The American Naturalist,' vol. xxxi. 

 no. 366, Juue 1^97, pp. 535-541. 



