MtscelJ<ineou8, 339 



The Developinent of the Intestinal Orer/arines of Marine Wonns. 

 By M. Louis L^ger. 



The Gregarines with a single segment, which are very frequently 

 met with living freely in the digestive tract of a large number of 

 Annelids, have hitherto been considered to be Monocystidea. 



The study of the development of Doliocustis nereidis, parasitic in 

 the intestine of Nereis cidtrifera, and of Doliooislis polydorce from 

 the intestine of Poh/dora Af/assizi, shows that these Gregarines are 

 in reality Dicystidea, exhibiting in their earliest youth the intra- 

 cellular stage, followed by a stage of budding which gives rise to 

 the Gregarine proper. During the budding stage the Gregarine 

 always exhibits two segments — the intra-cellular segment, or epi- 

 merite, and the extra-cellular segment, in which the nucleus is 

 contained. It is therefore at this moment only that the Gregarine 

 appears as a true Dicystid ; but this condition does not last long. 

 At a very early period the young individuals drop their epimerite 

 and become free in the intestine, when they exhibit all the cha- 

 racters of true Monoci/siis, with which they have hitherto been 

 confounded. 



In order to study the development of DoHocystis nereidis it is 

 necessary to examine with much care the elements of the epithelial 

 lining of the digestive tract of the Nereis, especially in its anterior 

 third. Individuals will then be met with which are extremely 

 young and still in the Coccidiid stage, th: t is to say, in the state of 

 a simple spherical nucleated mass, situated between the nucleus of 

 the cell and the surface. In the subsequent stages the primitive 

 Coccidiid has budded forth a segment, which makes its way into 

 the lumen of the digestive tract, and which is destined to form the 

 Gregarine proper. Finally, in a still more advanced stage the 

 Gregarine is definitively constituted ; the extra-ceUular bud has 

 considerably increased in size, and a layer of transverse muscular 

 fibrils has already become differentiated, while the intra-cellular 

 portion, on the contrary, is reduced to the condition of a simple 

 little knob (epimerite). Conditions such as this are met with pretty 

 frequently in the preparation, and we may even observe free indi- 

 viduals of which the epimeritcs are still capped with the shrivelled 

 epithelial cells ; this is the Cephalin stage, which is soon concluded 

 by the falling off of the epimerite, to give place to the stage of the 

 Sporadin. The Gregarine is henceforth free in the intestine, in the 

 form of an ovoid or elongated Monocystis, more or less drawn out 

 into a point at one of the poles. 



The development of Dolioq/stis poJydom, a new species which I 

 have met with in the Bay of Marseilles, takes place in precisely the 

 same manner ; only the epimerite is developed to a greater extent 

 than in the preceding species ; moreover it persists for a long time, 

 the result of which is that Cephalins of this species are commonly 

 encountered. This epimerite is in the form of an inverted frustum 

 of a cone, and it is directly continuous with the anterior extremity 



