644 ORDER PERITRICHA. 



coloured. Movements swift, rotating in alternate directions. Length 

 1-250". Hab.— Pond water. 



Examples of this species were abundantly developed in a sample of water con- 

 taining Eiiglena acits and Distig/napro/eies rtimtlQd. to the author by Mr. Thos. Bolton, 

 in November 1880. While at first sight presenting no inconsiderable resemblance 

 to detached VoriiceilcB, the recognition, on a more intimate acquaintance, of the pos- 

 terior location and conspicuous development of the anal aperture — from which the 

 passage of excreta was directly observed — together with the character of the oral 

 system, speedily indicated the necessity of assigning to this type a position altogether 

 independent of the Vorticellidae. Excepting, indeed, for the absence of an adherent 

 caudal appendage, it in many respects agrees with Urocentrum^ and may be most 

 conveniently referred to that family group. The likeness suggested is manifested in 

 addition to the number and position of the ciliary girdles and ventral location of the 

 oral aperture, in the texture and pale brownish hue of the parenchyma, and in its mode 

 of locomotion. This, while accomplished in a forward direction, is accompanied by 

 the rotation of the animalcule in alternate directions, a slight displacement of the 

 generated force being alone required to convert it into that oscilladng or pendulum- 

 like motion so highly characteristic of Urocentncm. While in most instances a single 

 subcentral contractile vesicle was alone to be detected, some few examples occurred 

 in which, as shown at PI. XXXIII. Fig. 11, two such structures were distinctly 

 developed. It would seem, however, to be by no means improbable that such zooids 

 were about to multiply by the process of fission, which, contrary to that of Urocen- 

 tnim, takes a longitudinal direction. It was remarked that the animalcules varied 

 very considerably among each other in their relative lengths and in the contour of 

 the posterior region. While more ordinarily the length nearly equalled twice the 

 breadth, the posterior extremity being in such case rounded or obtusely pointed, 

 examples were not unfrequently met with whose length did not surpass more than 

 one-half of the breadth, and the posterior extremity being abruptly truncate, the body 

 as a whole presented, as shown at PI. XXXIII. Fig. 12, a short discoidal contour. 

 Although the anterior ciliary wreath, with its thickened border, was in all instances 

 distinctly recognizable, the simple and smaller posterior girdle was not so clearly 

 perceived, and more often, indeed, presented the aspect only of a few lateral setose 

 appendages. At the end of a week's preservation in the living state all the 

 specimens received affixed themselves to the sides of the glass zoophyte trough to 

 which they had been transferred, and speedily entered upon the encysted state. 

 The band-like endoplast became subdivided into nodular fragments, but further 

 developmental phases were not observed. The remarkable homoplastic resem- 

 blance that subsists between the animalcules of this species and the so-called telo- 

 trochous larvae of certain Annelids, and which has suggested the generic title here 

 conferred upon it, is referred to, with an accompanying illustration, at pages 447 

 and 478 of the previous volume. 



The identification of this type with the Vorticella cratcriformis of O. F. Miiller, 

 figured and described by that authority close upon a century ago,* but which since 

 then up to the present time does not appear to have come within the notice of any 

 other investigator, has been quite recently and unexpectedly accomplished during a 

 final examination of the Miillerian species of Vorticella proper. The very clear 

 indication given in both Miiller's figures and accompanying text of the posteriorly 

 located anal aperture, added to all other details relating to contour, structure, colour, 

 and comportment in the water, has enabled the author to establish this identity in 

 the most conclusive manner, and to perpetuate a time-honoured specific title in place 

 of the new one which previously seemed unavoidable. In one of the figures given 

 by its original discoverer, /. c. pi. xxxix. fig. 7, an example of so-called conjugation 

 between two zooids is delineated, that must evidently be identified with the process 

 of longitudinal fission as observed by the author and figured in this treatise. 



Animalcula Infusoria,' p. 278, and pi. xxxix. figs. 7~13> 1/86. 



