690 ORDER PERITRICHA. 



attached to an independent pedicle, this type might have been identified with the 

 immature condition of Epistylis plicatilis, with which it agrees both in habitat and in 

 the apparent annulate character of the posterior extremity of the body identified by 

 Miiller with the pedicle in its contracted state. Should this species be rediscovered, 

 it will probably be found desirable to refer it to the author's newly instituted genus, 

 Rhabdostyla. 



Vorticella hians, Miiller, PI. XLIX. Fig. 41. Body elongate, pyriform or 

 lemon-shaped, widest and inflated posteriorly, about twice as long as broad ; pedicle 

 very short, scarcely as long as the body. Hab. Long-standing vegetable infusions. 



The above diagnosis and figure refer to what Miiller designates var. /? of Vorti- 

 cella hians, which is alone figured, and appears to be the most distinct form. In 

 more normal examples the pedicle equals three times the length of the body. 



GENUS VIII. CARCHESIUM, Ehrenberg. 



Animalcules ovate or pyriform, alike in shape and size, resembling those 

 of Vorticella, but united in social clusters, and forming compound dendritic 

 colony-stocks or zoodendria through repeated longitudinal fission, accom- 

 panied by the regular or irregular branching of their flexible primary 

 pedicle ; the muscular fibre within the compound pedicle not continuous 

 throughout, but interrupted at each bifurcation, so as to permit of the 

 independent extension and contraction of the separate zooids. The species 

 so far discovered mostly inhabit fresh water. 



The compound colony-stocks of the genus Carchesium, in common with those of 

 the genera Zoothamnium, Epistylis, and Opercularia, may be said to represent the 

 sum total of the normal fissive process of an ordinary Vorticella, but in which the 

 entire number of zooids so produced have, in place of becoming separately dispersed, 

 remained permanently united by their respective pedicles. The non-continuity of 

 the central muscular fibrilla, which permits the associated animalcules to contract 

 separately or in limited numbers on their compound footstalk, serves to distinguish 

 this genus from its nearest ally Zoothamnium. 



Carchesium polypinum, Lin. sp. 

 PL. XXXV. FIGS. 30, 31, AND 51, AND PL. XXXVI. FIGS. 1-8. 



Bodies conical-campanulate, somewhat gibbous, the anterior or peri- 

 stomal border dilated, revolute ; parenchyma transparent, colourless ; cuti- 

 cular surface smooth ; compound pedicle or zoodendrium not articulate, 

 subumbellate, consisting usually of an erect main rachis, from the summit 

 of which subtend a greater or less number of horizontal or oblique, simple 

 or ramifying branchlets which support the pedicellate animalcules, these 

 more usually exhibiting a unilateral plan of disposition. Length of bodies 

 1-570" to 1-430". 



HAB. Mostly fresh, but sometimes salt water. 



This species frequently occurs in ponds in such profusion as to form, as in 

 the case of Vorticella campanula and Epistylis grandis, a conspicuous, bluish-white, 

 mucilaginous film upon the surface of the water-plants or other objects to which 

 it may be attached. While among the commonest, it is undoubtedly one of 

 the most beautiful and luxuriantly growing representatives of the present family 

 group, the branching tree-like colonies, resulting from the multiple fission of a single 

 primary individual, often including as many as several hundred animalcules. Although 



