602 ORDER HETEROTRICHA. 



compared. Although thus demonstrating the essential distinctness of the two 

 genera ChcBtospira and Stichotricha, and the necessity of referring them to even 

 diverse orders of the Ciliata, the likeness between the two in both habits and in 

 certain important structural characteristics cannot be overlooked. This is most 

 prominently manifested in the peculiar form and deportment of the peristome and 

 in the custom of each to build and inhabit a mucilaginous or horny sheath. 

 These two generic types would appear to afford indeed but one among the many 

 instances that occur in demonstration of the close approximation to one another of 

 two seemingly widely diverse groups, as circumscribed by the necessarily artificial 

 boundaries of zoological taxonomy. 



Chsetospira Muelleri, Lachmann. Pl. XXIX. Figs. 37 and 38. 



Sheath or lorica flask-shaped, transparent, of horny consistence, the 

 enclosed animalcule adapting the contour of its body to the shape of the 

 lorica ; the spire formed by the flexure of the ligulate peristome describing 

 more than a single turn ; cilia of adoral fringe longest centrally, diminishing 

 gradually in length towards the apical and basal extremities ; fine, and 

 apparently retractile, setose cilia sometimes forming a conspicuous series 

 down the border of the peristome, opposite to that fringed by the adoral 

 cilia; endoplast spherical, subcentral ; contractile vesicle anteriorly situated. 

 Length of extended body 1-160". Hab. — Fresh and salt water. 



This species, while originally characterized as a fresh-water inhabitant occurring 

 only in the open cells of decaying leaves of Le?nna trisuka, has been met with by 

 the author under numerous varying conditions, not unfrequently with its transparent, 

 flask-shaped lorica independently attached to growing leaves of Myriophyllum and 

 other water plants, while on more than one occasion examples were encountered 

 that had built their habitations within the vacated egg-capsules of various species of 

 Rotiferse. Although Claparede and Lachmann have mentioned that it is only in 

 relationship with the following type that supplementary fine setae have been 

 detected upon the general surface of the body, these structures, as figured in the 

 accompanying illustration, have been frequently observed by the author in the present 

 variety. It seems highly probable that these supplementary setae, as in the case 

 of certain Stentors, are not of constant recurrence, but are extruded and retracted 

 at the will of their possessor. The contractile vesicle in the examples personally 

 examined occupied a much more anterior position than is given by Lachmann, 

 being indeed considerably in advance of the oral aperture and, as shown in the 

 accompanying illustration, in close vicinity to the distal termination of the lateral 

 membranous expansion, and to the first abrupt flexure of the peristome ; the systole 

 of this organ was found to recur with unvarying regularity every fifteen seconds. 

 The anal aperture is reported by Lachmann as occupying a position closely adjacent 

 to that of the contractile vesicle as here given. 



A species superficially so closely resembling C. Muelleri has been obtained by 

 the author from salt water that it is not thought desirable at present to introduce 

 it under a new title, this marine form being probably also identical with the 

 animalcule briefly described some years since by Dr. Strethill Wright under the 

 name of Chcetospira marina* 



Chaetospira imicicola, Lachmann. 



Sheath or lorica entirely mucilaginous, transparent ; the anteriorly pro- 

 duced lifTulate peristome forming, in the expanded state, less than a complete 

 spiral turn, the long adoral cilia that fringe its border being longest at the 

 * ' Quarterly Journal of Microscopy,' vol. ii. 1862. 



