GENUS URNULA. 807 



HAB. Fresh water, attached by the posterior extremity to the thoracic 

 limbs of Cyclops coronata. 



The contour of this singular animalcule, with its conical body and attenuate 

 tentaculate appendage, is, as remarked by Zenker, not unlike that of a Euglena, 

 or, perhaps, may be described as approaching still more closely that of Astasia 

 trichophora ; the tubular and suctorial character of the terminal appendage demon- 

 strates at once, however, its relationship with the ordinary Acinetcs. In this 

 connection it more especially accords with that developmental condition of Acineta 

 ferrum-equinum, described and figured by the same authority, in which a single 

 terminal suctorial tentacle only has made its appearance. The present species is of 

 comparatively rare occurrence, from twelve to twenty examples of the Cyclops in 

 question yielding, on examination, but one specimen of Rhyncheta. Treated with 

 reagents the parenchyma of this type contracts and separates from the investing 

 cuticle, which then presents the aspect of a delicate transparent lorica. 



GENUS II. URNULA, C. & L. 



Animalcules bearing a single retractile, simple or sparsely branched, 

 filiform tentaculate appendage ; excreting and inhabiting a sessilely attached, 

 membranous lorica. Multiplying by the production of free-swimming 

 ciliated embryos, and by the subdivision of the entire body-mass into 

 sporular elements. 



h 



Urnula epistylidis, C. & L. PL. XLVIII. FIGS. 1-4. 



Lorica transparent, gibbously ovate or urceolate, about twice as long as 

 broad, attached by a short obliquely developed attenuation of its posterior 

 region ; body nearly filling or occupying one moiety only of the cavity 

 of the lorica ; tentaculate appendage laterally developed, single filiform, 

 extensile for a distance surpassing twice the length of the body, usually 

 with one or two lateral branchlets, its substance distinctly granular ; con- 

 tractile vesicle single, subcentral ; endoplast unobserved. Length of 

 lorica 1-200". 



HAB. Fresh water, attached to the branching pedicle or zoodendrium 

 of Epistylis plicatilis. 



As originally figured and described by Claparede and Lachmann,* Urnula 

 epistylidis was referred to the group of the Rhizopoda, they being led by their 

 observations to regard the filiform tentaculate appendage of this organism as the 

 homologue of the pseudopod of a typical Rhizopod rather than as the tubular 

 suctorial organ of an Acinetan. That the position here assigned to it is the correct 

 one is, however, sufficiently proved by the more recent investigations of Stein, 

 Engelmann, and Wrzesniowski. The multiplication of this species through both 

 the production of ciliated embryos and by the resolution of the entire body into 

 spore-like elements is recorded by Claparede and Lachmann. The ciliated 

 embryos, produced singly from the parent body, are finely striate in an oblique 

 direction, and apparently completely or holotrichously ciliate. The existence of 

 these embryos constitutes of itself substantial evidence in support of the Acinetan 

 affinities of Urnula, no known Rhizopodal type developing cilia at any period of its 

 existence. 



* ' Etudes sur les Infusoires,' 1855. 



