698 ORDER PERITRICHA. 



Zoothamnium afflne, Stein. PL. XXXVI. FIG. 16. 



Bodies of animalcules ovate, twice as long as broad, somewhat con- 

 tracted posteriorly, truncate in front, and surmounted by a thick tumid 

 peristome of rather less diameter than that of the centre of the body ; 

 cuticular surface smooth ; pedicle very thick, dividing dichotomously, the 

 branches often attaining a nearly equal degree of elevation, but the general 

 contour varying considerably in different colonies ; surface of the pedicle 

 smooth during extension, but transversely plicate in the contracted state ; 

 endoplast semicircular, band-like, lying transversely with the axis of the 

 body ; no secondary spherical zooids. Length of individual 1-380" to 

 1-270". HAB. Fresh water, on aquatic insects and Entomostraca. 



The relatively abnormal thickness of the pedicle of this species serves to dis- 

 tinguish it readily from most other known forms ; while this structure is described 

 in its diagnosis as being perfectly smooth except in its contracted conditions, the 

 figures given by Stein, here reproduced, represent it with equally conspicuous 

 transverse plicae in both its extended and contracted states. The author has 

 recently, February 1879, met with small colonies of this animalcule attached to 

 the Amphipod Gammarus pulex taken from a running stream among Callitricha, 

 in the neighbourhood of St. Heliers, Jersey. In no instance were more than four 

 zooids attached to a single zoodendrium, while the greatest height of the latter 

 structure was less than that of the extended bodies. 



Zoothamnium parasita, Stein. PL. XXXVII. FIG. 16. 



Animalcules minute, ovato-fusiform, tapering posteriorly, scarcely one 

 and a half times as long as broad ; peristome-border thick, narrower than 

 the centre of the body ; ciliary disk slightly elevated ; cuticular surface 

 smooth ; a few, usually two, zooids only supported upon a short, smooth, 

 and comparatively slender, dichotomously dividing pedicle, whose entire 

 height does not equal that of a single zooid. Length of bodies 1-350". 



HAB. Fresh water, on Cyclops quadricornis and other Entomostraca. 



The form referred to this species by D'Udekem * and found on Asellus aquaticus, 

 would seem to be more correctly referable to the species last described. The bodies 

 of the zooids are comparatively larger and the pedicle thicker and more corrugate 

 than is reported by Stein of the present type. 



Zoothamnium nutans, C. & L. PL. XXXVI. FIGS. 9 AND 15. 



Animalcules few in number, one or two zooids only associated in a 

 single colony-stock, campanulate, slightly gibbous, attached obliquely to 

 a long, smooth, slender and articulate pedicle ; peristome-border widely 

 dilated ; surface of the cuticle finely and obliquely striate ; pedicle con- 

 tracting in a zigzag and not a spiral manner. Length of zooids 1-350". 



HAB. Salt water : Bergen (C. & L.). ; 



Zoothamnium aselli, C. & L. 



Animalcules elongate, subcylindrical, three times as long as broad, 

 attenuate posteriorly, attached in numbers to a very thick, smooth, inarticu- 



* 'Infusoires de la Belgique,' 1864. 



