340 ORDER CHOANO-FLAGELLATA. 



its origin. So far but a single colony of two animalcules has been met with by 

 the author, but there can be little doubt that it is identical with that uncertain form 

 figured by Stein in his ' Die Infusionschiere auf ihre Entwickelunggeschichte,' 1854, as 

 probably the young condition of one of the branching Vorticellidae, or rather as an 

 Acineta-phase, which he at that time believed preceded the perfect ciliated state of 

 those more highly organized Infusoria. The magnifying power employed by Stein 

 revealed only the two lateral margins of the transparent collar, which thus resembled 

 the semi-withdrawn suctorial fascicles of various typical Acineta. 



As many as ten zooids are comprised by Stein in the largest colony-stock he 

 illustrates. The single specimen encountered by the author was obtained from a 

 pond near South Norwood, London, in June 1877. 



Codosiga Steinii, S. K. PL. II. FIG. 20. 



Zooids evenly ovate, stationed singly, or during the process of sub- 

 division in pairs, at the extremities of a slender, dichotomously branching 

 pedicle or zoodendrium. Length of bodies 1-3000" ; primary, secondary 

 and succeeding subdivisions of the pedicle mostly equalling about twice the 

 length of the supported zooids. HAB. Fresh water. 



The above specific title is conferred upon the animalcule figured by Stein in 

 ' Wiegman's Archives,' Taf. ii. fig. 36, 1849, as the probable young of Epistylis 

 nutans;* these figures indicating, however, by the presence of the setum-like 

 process on each side of the anterior border, the possession of an imperfectly observed 

 but characteristic collar. In the illustrations of this form referred to and here repro- 

 duced, as many as fourteen zooids, in various processes of development, are repre- 

 sented upon the branching colony. The interspace between the basal attachment 

 and first division of the pedicle, as also those between its subsequent ramifications, 

 vary from the same to that of about twice the length of the body of the separate 

 zooids ; this more extended proportionate distance maintained between the ramifica- 

 tions of the pedicle readily distinguishes the species from Codosiga furcata, with 

 which the contour of this structural element most closely coincides. 



Codosiga assimilis, S. K. PL. II. FIG. 21. 



Zooids few in number, ovate or subpyriform, stationed singly at the 

 extremities of a branching pedicle, the main rachis of which, equal to 

 about four times the length of the zooids' bodies, is straight and simple, 

 dividing then in a dichotomous manner, and forming short ramifications 

 not exceeding the length of the animalcule's body. Length of these latter 

 1-1800". HAB. Fresh water. 



This type is likewise figured by Stein, in company with the two preceding forms, 

 as a probable early condition of Epistylis nutans, the mode of growth of the pedicle, 

 and proportionately larger size of the animalcules, indicating, however, its specific 

 distinctness. Pritchard, in reproducing Stein's figure, has proposed to identify it 

 '.vith the Epistylis (Codosiga) botrytis of Ehrenberg, but the compound ramification 

 of the distal region of the pedicle demonstrates its non-correspondence with that 

 simply pedicellate type. In this last named feature the pedicle of Codosiga assimilis 

 agrees more closely with that of C. grossularia, while the contour of the zooids 

 nearly resembles that of the marine Codosiga pyriformis. These latter are at the 

 same time of considerably larger dimensions than those of either of the last-named 

 varieties. 



By accident, the illustration of this species has been included in the index to 

 PI. II. as a second example of C. Steinii. 



* See also Pritchard's 'Infusoria,' pi. xxvii. fig. 22. 



