GENUS ZOOTHAMNIUM. 697 



This species as described by Wrzesniowski * is distinguished by the varied 

 character of the pedicle in its basal and distal regions, and by the abnormal size of 

 the contractile vesicle. This latter structure attains its fullest development in the 

 more abundant smaller zooids, and in which at full diastole it is of such large propor- 

 tions as to fill not only the ciliary disc, but to invade a large area of the parenchyma 

 beneath the peristome-border and in the neighbourhood of the pharynx. The con- 

 tractile fibrilla in this species commences a little beneath the junction of the smooth 

 basal with the wrinkled branching region of the pedicle, the entire colony-stock in 

 its state of contraction bending down obliquely from this point. The examples 

 supplying the type of this species were discovered by Wrzesniowski attached to 

 drifted seaweeds (Floridece) at Rugen in the Baltic. 



Zoothamnium dichotomum, Wright. PL. XXXVII. FIGS. 9-12. 



"Stem very regularly dichotomous ; pedicles long; zooids cylindrical, 

 resembling the fruit of the Rosa canina" 



The above brief diagnosis is simply reproduced as it appears in Pritchard's 

 ' Infusoria,' no dimensions or habitat that might assist towards the establishment of 

 its identity being furnished. The examples figured at PI. XXXVII. Figs. 9-12, as 

 presumably identical with the above-named species originally discovered by 

 Dr. Strethill Wright, were collected by the author in July 1879, ff the coast of 

 Falmouth, being dredged in company with Zoothamnium spirale from a depth of 

 about fifty fathoms. The colony-stocks thus obtained differed, however, from those 

 examined by Dr. Wright in the circumstance that zooids of two shapes and sizes 

 were developed on the dichotomously branching zoodendria. The majority and 

 smaller of these were simply campanulate, while it was only the few larger repro- 

 ductive units, produced mostly toward the bases of the branches, either singly or in 

 clusters of two or three, that coincided by reason of their ovate shape with the 

 foregoing diagnosis. As some few examples were met with in which while all the 

 ordinary campanulate animalcules had become detached, the larger ovate zooids 

 remained in situ, it would seem highly probable that the specimens upon which 

 Dr. Wright framed his brief description were similarly imperfect. It was observed 

 of the Falmouth specimens that while the normal campanulate zooids were, under 

 a magnification of two hundred diameters, perfectly smooth, the cuticular surface of 

 the larger ovate ones was very distinctly striate in a transverse direction. 



B. Zooms SIMILAR IN SHAPE AND SIZE HOMOMORPHIC. 



Zoothamnium gleniscum, C. & L. PL. XXXVI. FIGS. 24 AND 25. 



Animalcules pyriform, similar in shape and size, disposed alternately on 

 the parent branch ; their cuticular surface smooth ; pedicle finely striate 

 transversely, usually articulate at intervals about midway between each 

 subdivision. Dimensions unrecorded. 



HAB. Salt water, North Sea (C. & L.). 



This species is described by Claparede and Lachmann as closely resembling 

 Zoothamnium alternans, from which, however, it is to be distinguished by the more 

 slender articulate pedicle. The zooids are, moreover, estimated to be twice as large 

 as those of the last-mentioned variety, although their exact dimensions were not re- 

 corded. The articulations of the pedicle do not correspond with each bifurcation of 

 the stem as in the Carchesium epistylidis of the same authors, which it also closely 

 resembles, but one or more joints intervene between each such subdivision. 



'Zeitschrift fur Wissenschaftliche Zoologie,' Bd. xxix.. 1877. 



