158 PROCEEDINGS OF THE ACADEMY OF [PaRT I 



isolated, an Astasia (or Euglenaf) seeming identical, at first sight, 

 with the habitual parasite, but its paramylum grains were of a 

 more distinctly greenish hue, and besides a small red stigma could 

 be detected distinctly. On another occasion, I got from the in- 

 testine of a Cyclops an Astasia in which two small red eyes existed, 

 one to the right and the other to the left on the anterior part of the 

 body. This specimen, it must be added, was relatively broad and 

 short, and perhaps not far from dividing. 



That these two individuals belonged to Astasia mohilis is not 

 certain. Alexieeff observes that in the Euglena group "transitional 

 forms are found which lead from facultative to definitive para- 

 sitisms." Must Astasia mohilis be considered as a Euglena whose 

 evolution terminated in parasitism, and in which individuals may 

 be found, which retain some ancestral characters? 



Euglena pseudomermis sp. n. Plate VIII, flgxires 62, 63. 



This elegant little Euglena, which looks at first sight so much like a 

 Nematode that one sometimes mistakes it for one, was found in 

 two different localities, Pinchat and Rouelbeau, in every season of 

 the year but always very rare. 



The form is that of a needle (Plate VIII, fig. 62), 2° very straight, 

 165 to 190[x in length for only 73^ to 8[a in breadth, and it is quite 

 near the anterior part of the body, on a level with the contractile 

 vesicle, that the maximal breadth is found; from this region it di- 

 minishes in width by insensible gradation to the posterior extremity, 

 whose thinness is quite extraordinary. Owing to a slight lateral 

 compression, a transverse section of the needle would give a broadly 

 elliptical figure. Seen along the narrower of the sides, it shows a 

 characteristic swelling (Plate VIII, fig. 62), coinciding with the 

 dilatation of the internal reservoir. The periplast looks shining 

 and smooth, but in reahty proves longitudinally striated, but the 

 striae are so delicate and thin that only in very favorable conditions 

 can their reality be ascertained. At the anterior end (Plate VIII, 

 fig. 63), which is somewhat expanded, and in optical section appears 

 to be provided with two tips, the periplast curves and invaginates 

 towards the interior, but for a short distance only, and from this 

 point is continued as a simply plasmatic film which lines the reser- 

 voir. 



This characteristic pouch or reservoir, very long, broad and 

 rounded at the base, becomes narrower towards the top, and at 

 last joins the buccal opening. Into the hind part of the reservoir, 

 and on one of its sides, empties at regular times the contractile 

 vacuole, which is sometimes surrounded by very small accessory 

 vesicles. A short flagellum is seen arising from the buccal funnel, 



2° In the figure, the animalcule is represented too broad relatively to its length. 



