GENUS ZOOTHAMNIUM. 699 



late, dichotomously branching pedicle ; endoplast small, oval. Dimensions 

 of individual zooids unrecorded. Height of entire colony-stock 2 lines Fr. 



HAB. Fresh water : on Asellus aquaticus and various aquatic insects 

 and Crustacea. 



M. Claparede, in describing this species from the drawings only of M. Lach- 

 mann, remarks upon the very robust aspect of the animalcules, the outer cuticle 

 being more indurated than in any other known representative of the genus. In 

 this last respect, and also in the shape of the zooids, it is recognized by him as pre- 

 senting some resemblance to Epistylis plicatilis. It would seem to be by no means 

 improbable that the Carchesium asdli, subsequently described by T. W. Engelmann, is 

 identical with this form. 



Zoothamniuxn elegans, D'Udk. 



Bodies subpyriform, slightly gibbous ; the peristomal border widely 

 dilated, tapering and attenuate posteriorly ; pedicle slender, smooth, and 

 transparent, neither striate nor articulate, sparsely branching at its distal 

 extremity, supporting but a small number of zooids, which occupy a 

 closely approximate altitude ; ciliary disc projecting conspicuously beyond 

 the peristome-border ; pharyngeal cleft distinct, extending backwards 

 beyond the centre of the body ; endoplast ribbon-shaped, curved ; con- 

 tractile vesicle situated close to the entrance of the vestibulum. Length of 

 bodies 1-300". HAB. Salt and fresh water : Ostend (D'Udk). 



The occurrence of Amphileptus meleagris as a devouring parasite of the colonies 

 of this species, as first observed by Claparede and Lachmann, in association with 

 Epistylis plicatilis and Carchesium polypinum, was frequently observed byD'Udekem, 

 and receives attention in the description given of the above-named Holotrichous 

 animalcule. 



Zoothamnium macrostylum, D'Udk. PL. XXXIX. FIG. 30. 



Bodies elliptical or subcylindrical, about twice as long as broad, equally 

 rounded at the two extremities ; cuticular surface smooth, colony usually 

 consisting of two animalcules only, seated on a short, very massive, slightly 

 contractile, and longitudinally striate pedicle, whose height does not equal 

 that of the bodies of the zooids ; vibratile disc projecting but little beyond 

 the front border of the peristome ; endoplast rounded. Dimensions unre- 

 corded. HAB. Fresh water, on Asellus fluviatilis. 



This species would appear to closely resemble the Opercularia Lichtensteinii of 

 Stein. 



Zoothamnium pictum, From. 



Animalcules few in number, subspherical, smooth, hyaline, attached by 

 long pedicles to the slender main rachis, each zooid enclosing posteriorly 

 two green corpuscles. Length of bodies 1-1600". HAB. Fresh water. 



This form is so insufficiently described and figured by De Fromentel as to be 

 difficult to identify as a genuine Zoothamnium. While referring it to this genus its 

 describer hazards a doubt whether or not it is referable to the Vorticdla picta of 

 Ehrenberg, he having likewise a short while previously expressed uncertainty 

 concerning the identity of his newly introduced Vorticdla microscopica with the 



