702 ORDER PERITRICHA. 



branches attenuate, three or four times longer than the extended bodies, 

 the thicker and undivided basal portion comparatively short. Length of 

 zooids 1-280" to 1-145" 5 height of entire colony 1-9". 



HAB. Fresh water, attached to the shells of Mollusca, Limnceus 

 stagnalis, and various water-plants. 



This species may be easily recognized by the characteristic plicate or folded 

 contour of the posterior extremity of the zooids at the time of contraction, and by the 

 great relative length of the secondary divisions of the pedicle. The conjugation of 

 neighbouring animalcules of this species and the development from the endoplast of 

 ciliate embryos has been observed by Claparede and Lachmann ; illustrations of the 

 last-named phenomenon, reproduced from their drawings, are given at PL XXXIX. 

 Figs. 12-15. The branching pedicle or zoodendrium of Epistylis plicatilis frequently 

 gives support to colonies of a minute collared flagellate type apparently identical 

 with Monosiga Steinii. These may either completely encrust it with their aggre- 

 gated numbers or be distributed in isolated or scattered groups, as shown at a a in 

 PL XXXVIII. Fig. 6. 



Epistylis flavicans, Ehr. 

 PL. XXXV. FIGS. 48-50, AND PL. XXXVIII. FIGS. 1-5. 



Bodies in extension broadly campanulate, soft and flexible, widely 

 dilated anteriorly, subspherical when concentrated ; parenchyma usually of 

 a yellowish hue ; cuticular surface very finely striate transversely ; peri- 

 stome-border not thickened, much revolute, the ciliary wreath bearing five 

 or six convolutions of long, powerful cilia ; pedicle exhibiting two leading 

 modifications: in its younger and more robust phase dendriform, slender, 

 erect, profusely and dichotomously branching, the ultimate ramifications 

 short, not half the length of the zooids, widely divergent ; the older colonies 

 decumbent, the pedicle weak and straggling, rarely branching. Length of 

 zooids 1-192" to 1-70". HAB. Fresh water, on aquatic plants. 



Under the title of Epistylis flavicans is here included the E. flavicans and 

 E. grandis of C. G. Ehrenberg. Both Stein and Claparede and Lachmann ex- 

 pressed doubts concerning the specific independence of these types, and Professor 

 Wrzesniowski, with whom the author's investigations in this same direction accord, 

 has recently * brought forward conclusive evidence in demonstration of their identity. 

 As shown by this last-named authority, the type described by Ehrenberg under the 

 title of E, flavicans represents the earlier, erect, and more robust growth of the 

 animalcules, which in later generations lose their power of secreting a rigid stalk, 

 become larger and more turgid, and falling down develop a more or less matted, 

 horizontal layer of lax, thread-like, rarely dividing filaments, presenting under such 

 conditions all the characteristics of Ehrenberg's Epistylis grandis. Data of the 

 highest interest have been recorded by Greefff respecting the reproductive pheno- 

 mena of this species. By him, certain members of the erect colonies were observed 

 to become divided by fission into two, four, and ultimately into rosette-like groups of 

 eight minute, pyriform zooids, which developing respectively a posterior circlet 

 of cilia, were liberated into the surrounding water. These minute liberated zooids 

 were further observed to effect a junction, or to coalesce, with the ordinary attached 

 animalcules, fixing themselves to their sides, and penetrating into the substance of 



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

 t ' Archiv fur Naturgeschichte,' 1870. 



