404 GENEEAL HISTORY OF THE INTTJSORIA. 



a short, stout, respiratory tube, or, as it actually is, a depression surmounted 

 by a very elevated margin. In Notommata centrura (XXXYIII. 26 6), and 

 in N. Cojyeus, a long seta projects from a small elevation of the cuticle, on 

 each side of the back, having its extremity divided like a brush. The doubtful 

 cihated depression conceived by Prof. Huxley to be the nervous centre, belongs, 

 in Leydig's opinion, to the category of tactile fossae. 



Appendages of the Trunk. — The account already given of the cuticle and 

 lorica and their processes, leaves no special appendages of the trunk to be 

 described. Thus we have spoken of the spines from the anterior and posterior 

 margins of the lorica;, of those which, in a few examples, are produced from 

 its surface, and of the setae or cirrhi which extend from it in Anurcea hiremis, 

 in Notommata Copeus, and, on a larger scale, in Triarthra and Polyarthra 

 (XXXVIII. 30 c). 



The loseudopodium, or false foot, may either be accounted a production or 

 appendage of the trunk, or a distinct segment of the body. Its dimensions 

 and figure vary much in different species ; and in several it is entirely ab- 

 sent. It attains the highest development in Philodincea (XXXYIII. 1, 2), 

 where it consists of several progressively diminishing segments united by 

 shding joints, like the tubes of a telescope, and is analogous to the tails of 

 many Entomostraca, e. g. the Cydopidce. In this family, PhiJodincea, the body 

 tapers into the pseudopodium by a gradual lessening of the articulated seg- 

 ments ; so that the termination of the trunk proper and the commencement 

 of the process have no external indication, except what is supphed by the anal 

 orifice of the alimentary canal, which usually opens at the base of the tail. In 

 other families the termination of the trunk is more abnipt, and the distinct- 

 ness of the pseudopodium as a subordinate segment or member strongly pro- 

 nounced (XXXVIII. 25, 26). The high development of the organ gradually 

 diminishes, until the telescopic-jointed foot-process is degraded to the condi- 

 tion of one or two stifi' styles, supported on an enlarged base (XXXVIII. 22), 

 the intermediate stages being represented in various species (XXXVIII. 23, 

 24, 25, 31). In BracMonus, Colurus, Stephanops, and Dinocharis the foot- 

 process, although of three or more telescopic joints, is of much smaller 

 diameter, and depends like an appendage from the trunk, and is a transition 

 between this form and the usually tapering figiu-e of the PMlodina^a , as seen 

 in Rotifer macrurns, the trunk of which is abruptly attenuated into a long 

 foot. A further reduction of the many-jointed telescopic pseudopodium to 

 one or two joints, terminated by a single, double, or triple styliform or 

 pincer process, is exemplified in many Notommatce (XXXVIII. 26). in 

 Cydoglena, LepadeUa, Metopidia, Salpina, Diglena, Eospliora, Jlydatina 

 (XL. 1), Ratidus, &c., where the articulate structure is reduced to the 

 condition of an appendage of the trunk, its terminations assuming the chief 

 importance. Indeed, in some cases, one or two styliform processes seem to 

 be produced immediately fi^om the trunk without the intervention of an 

 articulated segment at the base (XXXIX. 1-3). At the same time a styh- 

 form foot-process is, as a rule, a very short pseudopodium supporting one or 

 more long styles. In the case of the less -developed or perfect tail-processes, 

 the section of the body is frequently attached obliquely to the trunk. 



In a very few examples the posterior dorsal surface of the body is pro- 

 longed as a true tail, having the pseudopodium fixed in front of it, the 

 anal orifice being between them. This is witnessed in Notommata Copeus 

 (XXXVIII. 26). 



The pseudopodium has in some genera styliform processes attached to 

 it throughout its length, as seen in the highly-developed telescopic pro- 

 longation of the PhiJodincea (XXXVIII. 1), in Callidina, Rotifer, Actinurus, 



