276 ORDER FLAGELLATA-PANTOSTOMATA. 



some representative of Dujardin's genus Hetcromita. The anterior extremity 

 of the body retains its pointed rostrum, and hkewise the two flagella; but the 

 function of these two organs becomes materially altered. Formerly the longer of 

 the two flagella was apparently the most actively employed ; this, however, is 

 now left trailing in the rear, while the shorter one is advanced to the front, 

 and, vigorously vibrating, constitutes the motive or propelling power. The move- 

 ments of the animalcule during this free-swimming condition are, however, by no 

 means regular, nor of long duration. After tumbling about in an aimless sort of 

 manner for a little while — say half an hour — it meets with some surface suitable 

 for attachment, and fixing itselL to it, gradually develops a lorica, pedicle, and all 

 other parts that characterize the parent form. In all such instances, where this 

 interesting growth from a detached zooid has been observed, it is worthy of remark 

 that the attachment was effected and the pedicle produced at that extremity which 

 previously bore the flagella, these organs being absorbed and developed anew at the 

 opposite or distal extremity. The peculiar aspect and movements of the free- 

 swimming zooids of Bicosoeca lacustris distinguish them readily from typical Hetero- 

 viitce or other independent forms, while their presence in the water affords a sure 

 indication of the close vicinity of the adult sedentary animalcules from whence, 

 by fission, they were originally derived. Not unfrequently Bicosoeca lacustris has 

 been observed by the author in a quiescent and apparently encysted state within 

 its lorica; while still more recently an example has been met with — PI. XVIII. 

 Fig. 18 — in which the former contents of the lorica were broken up into numerous 

 spore-like bodies. Empty loricae are of frequent occurrence, and are evidently of 

 considerable consistence. Although such a phenomenon has not yet been observed, 

 it is highly probable that the free-swimming monads Hberated by the process of 

 transverse fission, occasionally coalesce with one another, or with one of the fixed 

 examples, and thus give rise to the sporular encystments, in a manner identical with 

 what is now known to obtain among so many of the ordinary illoricate Flagellata. 

 A first record of the occurrence of this species on this side of the Atlantic, embody- 

 ing a figure illustrating the existence of two flagella — the second flagellum being 

 there described as a shorter stylate appendage — was communicated by the author to 

 the 'Monthly Microscopical Journal' for December 187 1. 



Bicosoeca gracillipes, J.-Clk. Pl. XVIII. Figs. 21 and 22, 



Lorica subcylindrical, slightly everted at the aperture, tapering towards 

 its junction with the pedicle, about three and a half times as long as broad ; 

 pedicle twice the length of the lorica ; enclosed animalcule elongate-oval, 

 usually entirely enclosed within the cavity of the lorica ; contractile vesicle 

 subcentral. Length of lorica 1-2000", of contained animalcule 1-4000". 



Hab. — Salt water. 



Tliis species was obtained by the author in September 1872, attached to seaweeds 

 and Polyzoa collected at Bognor, Sussex. The example represented at PI. XVIII. 

 Fig. 22, differs from the more typical form of growth in the shorter comparative 

 length of the pedicle which supports the lorica, and in the more exsert character of 

 the contained zooid. 



Bicosoeca tenuis, S. K. Pl. XVIII. Fig. 23. 



Lorica elongate-ovate or subfusiform, nearly three times as long as 

 broad, tapering equally at each extremity ; pedicle scarcely one-half the 

 height of the lorica; animalcule with an attenuate anterior lip-like projec- 

 tion, slightly exsert anteriorly. Length of lorica 1-3000" to 1-2500". 



Hab. — Salt water. 



