336 ORDER CHOANO-FLAGELLATA. 



eight or ten to twenty times that of the body of a single zooid. Contractile 

 vesicles and endoplast as in C. botrytis. HAB. Fresh water. 



This species, first figured and briefly described by the author under the above title 

 in the ' Monthly Microscopical Journal' for December 1871, represents, both as 

 regards the dimensions of the individual zooids and the size and proportion of the 

 branching pedicle, the largest, and at the same time one of the most symmetrically 

 developed members of this notably elegant genus so far discovered. An adult 

 colony, inclusive of the branching pedicle, not unfrequently attains a total height of as 

 much as the i-62nd part of an English inch, and is therefore easily recognized with 

 a comparatively low power of the microscope. It is almost beyond doubt a variety 

 of this species that is figured and described by Mr. Tatem in the ' Transactions of 

 the Royal Microscopical Society' for the year 1868, as a new type of Epistylis, and 

 which he proposes to distinguish by the title of Epistylis umbellatus. The magnifi- 

 cation of 300 diameters only, employed by Mr. Tatem, was not sufficient to enable 

 him to recognize the hyaline collar and flagellum surmounting the distal extremity 

 of each animalcule's body, but that he did not prove the existence of true cilia is 

 equally apparent on reference to his figures, where in place of the continuous ciliary 

 wreath characteristic of the ordinary Epistylids, a mere suspicion only of such 

 structure is indicated at the two antero-lateral margins, and which may be easily 

 identified with the imperfectly seen outline in profile of the transparent infundibu- 

 late collar. The dimensions, again, of the individual animalcules and branching 

 pedicle of Mr. Tatem's supposed Epistylis accord so closely with those of the species 

 now under discussion, that there can be but little uncertainty as to the near, if not 

 absolute, identity of the two forms, and on this account Mr. Tatem's proposed 

 specific title is here retained, and his own name associated with the nomenclature 

 of the species. The method in which the symmetrically branched pedicle of Codosiga 

 umbellata is produced is not very readily comprehended. The example figured by 

 Mr. Tatem would seem to afford an instance of a quadripartite branching variety, 

 but the tripartite one is the more prevalent. It might have been anticipated that 

 this quadripartite type would have been the most frequent as the resultant of 

 a single zooid twice divided by longitudinal fission, the four individuals thus pro- 

 duced then making a new start afterwards to repeat the process. The figure 

 supplied by Mr. Tatem in fact shows four individuals at the extremity of each of 

 the sixteen branchlets of the pedicle, a circumstance which exactly bears out such an 

 interpretation. In all cases examined by the author, however, the pedicle was 

 either tripartite or bi-tripartite (see PL IV. Figs, i and 3), the termination of each 

 branchlet bearing, moreover, a considerable number of collared zooids. The 

 foregoing explanation is therefore altogether inapplicable in these instances, and it 

 remains an open question whether this distinct order of growth is not possibly 

 indicative of a separate specific organization. Not having, however, as yet met 

 with the quadripartite form figured by Mr. Tatem, and thus obtained an opportunity 

 of instituting the necessary comparisons, the testimony so far elicited is here 

 accepted in favour of their specific identity, and they are here distinguished 

 as varietal forms only of Codosiga umbellafa. In the more frequent tripartite and 

 bi-tripartite pedicle of this specific type, it might in another direction be not inappro- 

 priately suggested that we find foreshadowed the same potential energy that pro- 

 duces in connection with the essentially similar collar-bearing monads of certain 

 calcareous and siliceous sponge-forms their characteristic tripartite or bi-tripartite 

 spicula. In addition to obtaining examples of Codosiga umbellata from various 

 localities near London, the author has also received it growing upon Anacharis 

 from the neighbourhood of Stourbridge, Worcestershire, in company with Oper- 

 cularia nutans and other Infusorial forms remitted by Mr. Thomas Bolton. 



Various altogether irregular stock-forms of this species are figured by Stein in 

 his recently published volume, one of the more prominent of these being repro- 

 duced at PL IV. Fig. 5. That authority has further conferred upon the present 

 species the distinct generic name of Codonodadium, with reference evidently to the 

 branched character of the supporting pedicle. The transition, however, from the 



