410 ORDER FLAGELLATA-EUSTOMATA. 



or separate pedicles. Animalcules elongate-ovoid, not exsert, attached to 

 the bottom of their respective lorica by a transparent elastic ligament. 

 Eye-like pigment-speck conspicuous. Length of separate loricae 1-1200", 

 of contained animalcules 1-2000". HAB. Pond water. 



This species, which may be regarded as the typical representative of the genus 

 Diitobryenjvi& received the attention of numerous authorities since its first discovery 

 by Ehrenberg. By no one of these, however, Stein and Biitschli excepted, does 

 its structure and affinities appear to have been correctly apprehended, a circum- 

 stance doubtless explained by the extreme minuteness of the individual animalcules 

 and the consequent necessity of employing the highest available magnifying powers 

 for their satisfactory determination. Hitherto this form has been regarded and 

 described as a uniflagellate type much resembling Euglena, and from which alone it 

 was chiefly distinguished by its compound protective lorica. Professor H. James- 

 Clark, apparently without a previous acquaintance with the type, refers to it, in 

 the course of his remarks on the genus Codonceca, as a " calyculated Euglenian." 



The first results that attended the author's examination of this elegant species, 

 in the year 1871, with a sufficient amplifying power, was the detection of two flagella, 

 one long and the other considerably shorter, in place of the single appendage pre- 

 viously ascribed to it, while it was at the same time elicited that the animalcules were 

 attached to the base of their respective lories; through the medium of a separate 

 retractile ligament. Those two points at once establish the near relationship that 

 exists between this form and the genus Epipyxis. The compound colony-stocks of 

 Dinobryon sertularia are frequently met with containing no fewer than fifty to sixty 

 separate loricae, which are so united to one another as to present as a whole a 

 remarkable resemblance in miniature to the polyparies of certain of the Polyzoa or 

 Sertularian Zoophytes. The adult colonies thus constructed are usually found pro- 

 gressing through the water with a rolling action and considerable velocity, being 

 propelled by the rapid vibration of the innumerable flagella. In its younger state 

 it is however an essentially sedentary form, the primary zooid with its investing 

 lorica being attached to some fulcrum of support, as in other ordinary pedicellate 

 types here described. As the colony develops, the lower or primary cells become 

 atrophied, much in the same manner as the lower portion of the branch of a 

 madreporic coral, and these deserted cells being unable to bear the weight of the 

 superincumbent mass, snap off", and thus release the colony into the surrounding 

 water under those conditions which are most usually met with. No process of 

 reproduction in Dinobryon sertularia has been yet observed in addition to the 

 ordinary one of oblique fission, as in Epipyxis. The resultant of such fission, how- 

 ever, in most cases, instead of swimming off to form the foundation of a new settle- 

 ment, attaches itself just beneath the margin of the aperture of the parent lorica, 

 and then builds up a corresponding domicile. This process in the course of a few 

 generations results in the formation of the elegant compound polythecium charac- 

 teristic of the adult colony. 



Both Biitschli and Stein have recently recorded the production by this animalcule 

 of spherical encystments, as represented at PI. XX. Figs. 38-40 ; it is a remarkable 

 fact, however, that the well-developed posterior ligament or footstalk, by the con- 

 traction of which the zooids are enabled to retreat rapidly to the further confines of 

 their loricae, has not been distinctly recognized in this species by either of these 

 authorities. The oral aperture, according to Stein, is immediately adjacent to the 

 point of insertion of the two flagella and scarcely to be distinguished from the eye- 

 like pigment-speck. 



Dinobryon stipitatum, Stein. PL. XXII. FIG. 41. 



Loricae elongate, trumpet-shaped, widest and slightly everted anteriorly, 

 tapering, attenuate, and acuminately pointed posteriorly, the Jotal length 

 equalling seven or eight times the greatest breadth ; zooids elongate-ovate, 



