576 ORDER HETEROTRICHA. 



of the contour border to the middle of the ventral side ; no tremulous flap ; 

 pharynx very long, funicular, bent towards the left, and forming an 

 immediate continuation of the peristome excavation ; adoral ciliary wreath 

 very broad, much concealed, lying completely within the peristome cleft ; 

 the cilia of general surface very fine, disposed in longitudinal rows ; anal 

 aperture postero-terminal ; endoplast band-like, cur\-ed or sinuous ; con- 

 tractile vesicles distinct, usually multiple. Inhabiting fresh water. 



By writers previous to the time of Stein and Claparfede and Lachmann the 

 genus Bursaria has been made to include a vast number of widely diverse infusorial 

 forms, now distributed, with one or two exceptions, among the genera Plagiotoma, 

 Nyctotherus, Leucophrys, Ophryoglma, Balantidium, Paramacium, and Opalina. It 

 thus happens that out of a score or more of animalcules associated with the title 

 of Bursaria by Ehrenberg, and included in Pritchard's ' Infusoria,' one species 

 only, the Bursaria truucaUlla of Miiller, is now left to represent the genus. 



Bursaria tnincatella, Miiller. Pl. XXIX. Figs, i and 2. 

 Body broadly ovate, purse or sac-shaped, the ventral border flattened, 

 the dorsal one convex, scarcely half as long again as broad, widest pos- 

 teriorly, narrowed slightly at the truncate anterior extremity, the frontal 

 angles rounded, the margin of the right side convex, usually longer than 

 that of the left, the margin of the shorter left side slightly concave ; endo- 

 plast band-like, flexuose; contractile vesicles minute, spherical, many in 

 number, distributed throughout the substance of the cortex. Length 'oi 

 body 1-4S" to 1-36". Hab. — Pond and marsh water. 



As originally figiu-ed by Ehrenberg, this species is represented as possessing but 

 one large terminal contractile vesicle, and Claparfede and Lachmann, adopting the 

 view of Lieberkuhn, have accordingly considered it desirable to recognize the many- 

 vesicled form as a distinct species under the title of Bursaria decora. It is main- 

 tained, however, by Stein that in all details of form and structure the two animal- 

 cules so essentially agree with each other that their separation as two distinct species 

 cannot be recognized. Supposed embr)'os of this animalcule, PI. XXIX Fig. 2, 

 were obsen^ed by Stein to the number of from thirty to as many as two hundred 

 inside a single adult These embrj'os were simply ovate, clothed all over with 

 fine cilia, a minute tubular prominence being developed at the anterior extremity. 

 The accredited parent Bursaria, in certain of these instances, was observed to be in 

 a quiescent condition, perfectly ovate in form, and having all trace of the peristome 

 and oral fossa obliterated. Singularly to remark, however, the endoplast was still 

 present in its characteristic band-like form ; this last-named circumstance justifies 

 a doubt as to whether or not these so-called embr}'os were parasitic organisms, and 

 more especially since their further development into t}'pical Bursaria was not traced 

 by Stein. From Condylostoma stagnalis and Leucophrys patula, which at first 

 sight, perhaps, presents a considerable resemblance to it, Bursaria truncaiella may 

 be readily distinguished by the extraordinary development of the pocket-Uke oral 

 fossa. The present species is apparently by no means a cosmopolitan form, but 

 where found usually occurs in considerable abundance. The author has recently 

 obtained this fine animalcule through Mr. Thomas Bolton from the neighbourhoods 

 of Stourbridge and Birmingham. It was observed of the examples from the last- 

 named locality that the ordinary contour exhibited was compressed, curv-ed, and 

 elongate to an extent that clearly assimilated them to the characteristic shape of 

 Leucophrys patula, as delineated at PI. XXIX. Fig. 18. The ixa3S!itx Bursaria vorti- 

 cella of Ehrenberg is held by Stein to be identical with the younger and immature 

 conditions of B. truncaiella. 



