GENUS BICOSCECA. 



277 



This species has been obtained on filamentous algce and Sertularian zoophytes at 

 St. Heliers, Jersey, and lilcewise at Bognor, Sussex. Both the lorica and contained 

 animalcule, while presenting a considerable resemblance to the common fresh-water 

 type B. lacnstris, are to be distinguished from the same by their more attenuate 

 contour. The development of this type from a naked P/iyso/no/ias-WkQ form has been 

 observed, the subsequently produced lorica first appearing as a mere bubble-like 

 film round the anterior margin of the animalcule's body. 



Bicosoeca pocillum, S. K. Pl. XVIII. Figs. 25-29. 



Lorica cup-shaped or subcyliiidrical, rounded posteriorly, the anterior 

 margin abruptly truncate, neither everted or constricted, varying in height 

 from one and a half to two or three times its greatest breadth ; pedicle 

 short, rarely half as high as the lorica ; animalcule subovate or calceo- 

 late, rounded posteriorly, the anterior margin excavate, produced on one 

 side as a broad, flattened, lip-like process, occupying from one-third to 

 one-half of the cavity of the lorica ; posterior retractile ligament equalling 

 the body in length ; contractile vesicle posteriorly situated ; endoplast 

 spherical, subcentral. Length of lorica 1-2500" to 1-1500", of contained 

 animalcule 1-3250". 



Hab. — Salt water attached to the polyparies of hydroid zoophytes 

 and polyzoa. 



This species was obtained abundantly by the author at St. Heliers, Jersey, in the 

 summer of the year 1878. It may be readily distinguished from all the preceding 

 members of the genus by the rounded and subcalceolate contour of the animalcule 

 and the plain cup-like or subcyhndrical shape of the protective sheath. Multipli- 

 cation by transverse fission was frequently observed, the free-swimming zooid 

 produced by this process presenting a somewhat variable but highly distinctive 

 form. In certain instances — PI. XVIII. Fig. 27 — the posterior region of the body 

 was symmetrically rounded, as in the parent monad, but in others (Fig. 28) drawn out 

 in an attenuated tail-like manner. The longer or primary flagellum under these free- 

 swimming conditions was always extended in advance, causing by its undulations an 

 even motion in a straightforward direction, while the shorter and secondary 

 flagellum, about half the length of the primary one, was reflected ventrally, and 

 trailed in the rear in a manner that imparted to the animalcule, as in the case of the 

 similar motile zooid of Bicosoeca lacustris, a close resemblance to the members of 

 the genus Heteromiia. Encountered in this free-swimming condition only, the 

 animalcule would, indeed, without the slightest inconsistence, be referred to the last- 

 named genus. The motile animalcules, after a brief nomadic existence, were observed 

 to attach themselves, and to gradually develop, by exudation, their transparent 

 lories. In the fixed condition immediately preceding the secretion of this protective 

 structure, or in which the body had developed only its thread-like pedicle, as shown 

 at PI. XVIII. Fig. 29, the general form and structure correspond, to all appearances, 

 with those of a typical representative of the genus Physomonas. The developmental 

 history of this type is thus shown to exhibit three widely distinct phases, each of 

 them being characteristic successively of the normal or adult condition of the three 

 distinct Flagellate genera Hctcromita, Physomonas, and finally Bicosoeca. There is 

 doubtless a still earlier and more simple monoflagellate condition resulting from the 

 breaking-up of the parent body into spores, to be discovered. The ingestion of 

 food at various parts of the periphery was frequently observed. 



Examples of this species have been recently received by the author, in company 

 with other marine Infusoria, from Mr. Thomas Bolton's microscopical studio. 



