444 ORDER CILIO-FLAGELLATA. 



that the body is transparent or bluish-white, with a sharply denned red eye-like pig- 

 ment-speck, a long flagellum, and very delicate ciliary girdle ; the body was usually 

 observed to contain a greater or less number of devoured Chlamydomonas monad ina. 

 By a careful examination a round light spot was detected near the point of junction 

 of the characteristic equatorial and longitudinal body grooves, which apparently 

 betokened the oral aperture; the long flagellum was inserted close to this oral 

 fossa. Stein had previously provisionally conferred upon this type the name of 

 Peridinium vorticella, but recognizes in his most recently published volume its 

 probable identity with Perty's type. 



Gymnodinium marinum, S. K. PL. XXV. FIGS. 60 AND 61. 



Body subspheroidal or trilobate from the dorsal or ventral aspect, 

 kidney-shaped, with a convex dorsal, and concave ventral surface, as seen 

 in profile ; flagellum conspicuous, its length equalling twice the diameter 

 of the body ; endoplasm transparent, usually enclosing numerous spheroidal 

 corpuscles ; oral aperture distinct. Diameter i-iooo". HAB. Salt water. 



This species was obtained abundantly by the author in an infusion of hay in sea- 

 water made at St. Heliers, Jersey, in February 1879, an ^ a ft er tne expiration of 

 just one month from the first preparation of the maceration. The motions of the 

 animalcule in the water were rapid and oscillating, and its habits eminently predatory, 

 closely resembling those of Dinomonas. As observed of the two species of the last- 

 named genus, it was continually engaged in chasing and devouring the smaller Hetero- 

 tnita and other monads contained in the same infusion, its oral aperture during the 

 engulfment of its captured prey, as shown at PI. XXV. Fig. 61, being expanded 

 and conspicuously indicated. It would seem just possible that the Peridinium monas 

 of Ehrenberg, briefly described as " very small, obtuse, without horns, remarkably 

 social. Diameter 1-1728". Hab. Baltic Sea," may be identical with this species. 



Gymnodinium Lachmanni, S. K. PL. XXV. FIGS. 58 AND 59. 



Body elliptical, twice as long as broad, equatorial groove very oblique ; 

 endoplasm transparent, enclosing spheroidal corpuscles. Length 1-600". 

 HAB. Salt water. 



This species is simply recorded by Claparede and Lachmann as a minute Peri- 

 dinium, encountered in salt water on the coast of Norway. Its relationship to the 

 other members of the present genus is obvious, though at the same time it differs, 

 in its greater proportionate length and in the conspicuously oblique direction of the 

 equatorial groove, from the marine form previously described. 



Gymnodinium roseolum, Schmarda sp. PL. XXV. FIG. 53. 



Body elliptical ; segments uneven ; flagellum indistinct ; colour pale 

 pink ; enclosing an eye-like pigment-spot. Length 1-720". 

 HAB. Fresh water. 



Described by Schmarda * as a species of Glenodinium. Incepted Chlamydo- 

 monads and other food-material were observed by its discoverer. 



The Peridinium inerme, a minute subspheroidal form (PI. XXV. Fig. 54), and 

 the Peridinium incequale, having conspicuously narrow segments, of the same writer, 

 are apparently identical with the Gymnodinium monadicum and G. corpusculum 

 previously described. 



* " Zur Naturgeschichte Egyptens," ' Denkschrift der Kaiser. Akad. der Wiss. Wien, 1854.' 



