278 ORDER FLAGELLATA-PANTOSTOMATA. 



GENUS III. STYLOBRYON, De Fromentel. 



Animalcules social, inhabiting a compound polythecium, composed of 

 separate horny loricae united to one another, or to a common pedicle, 

 through the medium of slender independent footstalks ; bodies ovate 

 with a projecting lip-like anterior border, affixed to the bottom of their 

 loricae by a contractile thread-like peduncle ; flagella two in number, 

 uneven, one long and one short, the former rolled spirally when retracted ; 

 parenchyma transparent and homogeneous. Increasing by transverse 

 subdivision and by the resolution of the body into spores. 



HAB. Fresh water. 



Stylobryon petiolatum, Duj. sp. PL. XXIII. FIGS. 17-30. 



Component loricae of polythecium wineglass-shaped, widest and slightly 

 everted anteriorly, tapering towards and conically pointed at the posterior 

 extremity, from one and a half to three times as long as broad ; united 

 to each other by pedicles which, while subequal in the same polythecium, 

 vary in diverse colony-stocks from less than one-half to three or four 

 times the length of a single lorica ; pedicles produced for some little 

 distance within the cavity of their associated loricae, and forming bases of 

 attachment for the enclosed zooids ; animalcules plastic and changeable in 

 shape, irregularly ovate, with one of the antero-lateral angles projecting 

 in a lip-like manner, occupying about one-half of the cavity of the loricae, 

 united to it posteriorly by a contractile thread-like peduncle ; flagella two 

 in number, one long and one short, inserted at the base of the anterior lip- 

 like prominence, the longer one coiled spirally when retracted ; contractile 

 vesicle single, posteriorly located ; endoplast spherical, subcentral. Length 

 of loricae 1-800" to 1-500". 



HAB. Pond water, multiplying by transverse fission and by the sub- 

 division of the entire body into spores. 



This animalcule was first described by Dujardin under the title of Dinobryon 

 petiolatum, the generic one here given being conferred upon it by De Fromentel, who 

 figures and describes it in his ' Microzoaires ' as Stylobryon insignis. There can 

 further be but little doubt that the species figured by Stein in his recently published 

 volume under the name of Poteriodendron petiolatum represents the same form, and 

 this notwithstanding there are certain remarkable structural features accredited to it 

 by this authority which, if fully substantiated, would necessitate its recognition as an 

 entirely distinct organic type. According to Stein, the loricae, while corresponding 

 entirely in their contour and mode of union as defined in the above diagnosis, 

 contain animalcules possessing one flagellum only, but which bear in the anterior 

 region and to one side of the flagellum a supplementary membraniform expansion, 

 resembling in a less conspicuously developed degree the funnel-shaped collar of 

 the Choano-Flagellata. Having, however, had the opportunity of examining an 

 extensive series of examples of the form now under discussion obtained from diverse 

 localities, the author has arrived at the conclusion that so far as the presence of a 

 collar-like structure is concerned, Stein has misinterpreted the actual facts of the 

 case. In no instance could any such independent organ be detected ; but in place 

 of this it was observed that the anteriorly developed lip-like prominence occupied 



