446 Dr. Henri Blanc on Ceratiura hirundinella. 



Treated with osmic acid, chromic acid, or picro-sulphuric 

 acid, the Ceratia of the Lake of Geneva show an exoplasra 

 which is not homogeneous, as described by M. Bergh in Gera- 

 tium and Peridinium ; it is rather vacuolar in the species 

 under consideration (fig. 5, ex). The endoplasm (fig. 5, ew), 

 which is denser, contains verj fine granules, large and small 

 globules of a green or yellow colour, or even red, and, lastly, 

 other colourless, but very refractive, globules. Of the green 

 and yellow globules the former are the more numerous ; this 

 abundance of green globules always gives the living Ceratia 

 a well-marked greenish coloration, which is produced by 

 chlorophyll. The quantity of yellow globules varies much 

 in different specimens ; M. Bergh ascribes this coloration to 

 the presence of diatomine. The red globules are much more 

 rare than the preceding, and frequently their presence cannot 

 be recognized ; when they exist there are only one or two of 

 them. These red globules are very large, always placed near 

 the ventral orifice (figs. 5 and 6, gl. r.). After the application 

 of the reagents mentioned above they contract, generally 

 leaving around them a well-defined vacant space ; each globule 

 then appears as if contained in a vacuole. M. Bergh, who 

 observed these red globules in Ceratium comutum, regards 

 them, I believe rightly, as being of an oily nature, and ascribes 

 to them a part in the act of assimilation. As to the refractive 

 colourless globules which are observed in all specimens 

 (fig. 5,^?. g.\ they are of a fatty nature, for they are imme- 

 diately coloured brown by osmic acid. 



The nucleus of the Ceratia of the Lake of Geneva is of an 

 oval form (figs. 5, 6, n) ; it occupies nearly the middle of the 

 body, and its longer axis is most frequently parallel to the 

 cincture. It is 0"030 millira. long by O'OIO millim. broad ; 

 it possesses a spherical nucleolus placed excentrically, 0'003 

 millim. in diameter (fig. 5, nii). The intimate structure of 

 the nucleus and nucleolus varies according to the histological 

 reagents employed. In specimens fixed by chromic acid and 

 stained with picrocarmine, the nucleus appears to be finely 

 granulated, and the nucleolus like a small homogeneous 

 refractive body, absorbing more of the colouring substance 

 than the rest of the nucleus (fig. 5). In other specimens 

 fixed by picro-sulphuric acid and coloured with acetic car- 

 mine, the chromatic substance of the nucleus appears in the 

 form of small bacilli held in suspension in the nuclear liquid 

 without forming a network of any kind (fig. 5 his) ; the 

 nucleolus, instead of being a well-coloured refractive body, 

 has precisely the aspect of a vacuole or of a rounded colourless 

 body (fig. 5 liis^ nii). The nuclear membrane, which is ex- 

 cessively thin, is always visible. 



