664 ORDER PERITRICHA. 



design. In Spirochona Sc/ieuteni it forms a simple uniform horizontal coil of but 

 one revolution, whose greatest altitude scarcely equals one-quarter of the height 

 of the body, and with which its greatest width is at the same time subequal. In the 

 present type there are two distinct revolutions to the membranous funnel, the inner 

 and lesser one projecting a considerable distance beyond the margin of the external 

 or basal one, whose height attains to or exceeds one-half of the length of the entire 

 body, while its diameter at its anterior and everted edge equals no less than twice 

 that of the subjacent body. The character of the fimbriation of the anterior border 

 of the external or basal revolution of the membranous funnel is very remarkable. 

 As developed in Spirochona Scheutaii such fimbriation is represented by Stein as 

 forming a series of less than a score of equal-lengthed setiform processes which 

 extend along one side only of the expanded structure. In the present species the 

 homologous elements are developed throughout the whole extent of the basal revo- 

 lution of the funnel, and are, moreover, of two distinct lengths, numbering fifty or 

 sixty in all, every fifth element being over twice the length of the four uniform and 

 comparatively short intervening ones. The entire circle is thus geometrically sub- 

 divided after the fashion of the dial of a watch, or suggests perhaps still more 

 significantly the delicately ruled and similarly proportioned subdivisions of a micro- 

 metric scale. Taken in their entirety, the contour of an animalcule of this species, 

 with its fusiform body and expanding fimbriated funnel, is not unlike that of the 

 seed and attached pappus of certain plants, such as Valerian or many of the Com- 

 positae. Earlier conditions of this type, in which the funnel was yet undeveloped, 

 were frequently met with, but in no instance could there be detected an example of 

 lateral gemmation as obtains in the preceding form and in various species of 

 Spirochona, 



Genus V. RHABDOSTYLA, S. K. 

 (Greek, rhabdos, rod ; stulos, stem.) 



Animalcules solitary, resembling those of Vorticclla, but seated on a 

 rigid, unretractile instead of a flexible, contractile pedicle. 



This new genus has been instituted for the reception of a series of animalcules, 

 several of which have at the time of discovery been described as solitary members 

 of the genus Epistylis. Their position relative to the last-named group, however, is 

 evidently parallel to that which subsists between the solitary genus VorticcUa and 

 the compound type of the same form distinguished by the title of Carchesium. 

 The majority of the species so far discovered are inhabitants of fresh water, and are 

 mostly remarkable for the extreme shortness of their rigid footstalk ; in but two 

 instances only does this structure exceed the length of the animalcule's body. 



Rhabdostyla ovum, S. K. Pl. XXXIV. Figs. 5 and 6. 



Body ovoid, truncate anteriorly when expanded, attached to a slender 

 rio-id pedicle of about one-quarter of its own length ; the surface of cuticle 

 delicately striate transversely ; ciliary wreath forming two circlets, cilia 

 very long and strong ; endoplast band-like, curved, disposed longitudinally. 

 Length of body 1-500". Hab.— Fresh water. 



This species was obtained by the author in some abundance on aquatic plants 

 from a pond in the neighbourhood of Stoke Newington, London. The band-like 

 endoplast, as shown in the accompanying illustration, was conspicuously developed. 

 When disturbed or not feeding it closed its peristomal border up tightly, presenting 

 under such circumstances a perfectly ovoid contour. On several occasions it was 

 observed, when thus contracted, to rapidly jerk its body backwards and forwards 

 upon its short pedicle, as though irritated or trying to free itself from some obstruc- 



