588 ORDER HETEROTRICHA. 



thiere,' 1838, and which form he further pronounces to be properly referable to the 

 Holotrichous order, differing from the type as here recognized only, but at the same 

 time essentially, in the non-possession of a fringe of larger adoral cilia or cirri. 

 On consulting the works cited, however, the author has been able to recognize the 

 presence of these differentiated cilia in every instance, such circumstance rendering 

 the retention of Stein's genus Climacostomum undesirable. If, as Professor Stein 

 maintains, an animalcule exists which agrees with his so-called Leucophrys patula 

 in the absence of specialized adoral cilia, such type is not referable to the Leucophrys 

 of Ehrenberg, and will have necessarily to be relegated, in his promised monograph 

 of the Holotricha, to a new genus. 



In both general contour and variation of colour Leucophrys patula resembles in a 

 remarkable manner contracted examples of Stentor polyiuorphus, for which type 

 at a first glance it might easily be mistaken. From such, however, it is readily dis- 

 tinguishable by the posterior location of the anal aperture and contractile vesicle, 

 and by the less complete circle formed by the ciliary spire. Notwithstanding these 

 differences, however, the present type evidently represents a link of connection 

 between the families of the Stentoridae and Spirostomidae, uniting with the same 

 the characteristics of the Bursariidse as exhibited in the genus Balantidhim. By 

 Perty, ' Kleinsten Lebensformen,' 1852, the green and colourless varieties of this 

 species are figured and described under the title of Bursar ia vircns and B. patula. 



Fam. III. STENTORIDiE, Stein. 



Animalcules free-swimming or temporarily adherent, highly elastic and 

 contractile, more or less elongate and cylindrical ; often inhabiting, either 

 singly or socially, a mucilaginous or indurated sheath or lorica ; the entire 

 frontal border embraced by the peristome ; peristome-field circular or pro- 

 duced into a single central spiral or two lappet-like lateral prolongations ; 

 oral aperture perforating the margin or deeper confines of the peristome- 

 field ; larger adoral cilia or cirri describing a complete dextrotropous or 

 right winding spire \ anal aperture situated anteriorly immediately beneath 

 the peristome. 



Genus I. STENTOR, Oken. 



Animalcules sedentary or freely motile at will, in the former case attach- 

 ing themselves by their softer adherent posterior extremity to sub- 

 merged aquatic objects, sometimes secreting a mucilaginous investing 

 sheath ; bodies highly elastic and variable in form : when swimming and 

 contracted, clavate, pyriform or turbinate ; when fixed and extended, trumpet- 

 shaped, broadly expanded anteriorly, tapering off and attenuate towards 

 the attached posterior extremity ; peristome describing an almost complete 

 circuit around the expanded anterior border, its left-hand extremity or 

 limb spirally involute, forming a small infundibulate or pocket-shaped fossa, 

 which conducts to the oral aperture, the right-hand limb free and usually 

 raised considerably above the opposite or left-hand one ; peristomal cilia 

 cirrose, very large and strong ; cilia of the cuticular surface very fine, distri- 

 buted in even longitudinal rows, occasionally supplemented by sparingly 

 scattered hair-like setae ; endoplast band-like, moniliform or rounded, 

 contractile vesicle usually complex, consisting of an anterior circular dila- 



