| OCR Text |
Show 356 MR. F. E. BEDDARD ON A N E W GREGARINE. [June 5, with individuals of the next stage ; this is characterized by its size and rather more complicated structure. The general form of the body is, however, the same. The drawing (p. 357) illustrates this stage, as well as the encysted condition to be presently described. The upper part of the figure represents an individual of the second stage ; the lower part illustrates the encysted condition, in which the whole Gregarine is enclosed by a cyst which is limited in the figure to the lower process. In the second stage the body is limited externally by a clear membrane of some thickness, which is probably the cuticle ; the coarse granules which fill the interior of the parasite are sometimes restricted to the globular part of the body, and are sometimes also found in one or both of the slender processes. These differences are, however, probably due to movements in the protoplasm of the living Gregarine, which has been arrested at various intervals. The surface of the two processes, and probably of the whole body, is covered with delicate fibres, which generally run obliquely to the long axis of the process, as is shown in the diagram (b). Careful focusing shows these fibres to be quite superficial, and they are therefore probably cuticular. During this stage, and also in the earlier stages, the Gregarine multiplies by transverse fission-a process rare among the Gregarinida1. The extremity of one of the processes becomes swollen and filled with the granules of the entoplasm. This swelling increases in size until it equals the body of the parent; a process grows out from the end opposite to that by which it is attached to the parent; these two then probably separate. In the third stage the body of the parasite is covered externally with a remarkable cyst. Individuals in the encysted condition were only met with in the substance of the vesiculae seminales of the Perichceta. The structure of the cyst-membrane is illustrated in the lower half of the drawing (c). It is of great thickness upon the one or two processes into which the body of the Gregarine is prolonged ; it is, however, much thinner upon the spherical region of the body. The main mass of the cyst has a fibrous appearance, and imbedded in it are numerous bodies which I cannot but regard as nuclei; these latter were evident in transverse sections, as well as in glycerine preparations of the entire parasite. The presence of nuclei in the cyst leads me to infer that the latter is not (at any rate entirely) formed by the parasite; the fibrous portion of the cyst, on the other hand, looks as if it were an hypertrophied condition of the fibroid investment found in the free living parasites of the ccelom described above as stage 2. In some of the encysted parasites there was a single large nucleus (a) ; in others a large number of smaller nuclei; this condition is no doubt preliminary to sporillation. Karyokinetic figures were observer. in the dividing nuclei. 1 Figured by Ruschhaupt (Jen. Zeitschr. 1885, Taf. xxii. fig. 13) in Mono-cystis porrecta. |
