EYE-SPOT AND PLAGELLUM IN EUGLENA VIEIDIS. 473 



of the question will be found in the first volume of the ' Traite 

 de Zoologie Concrete ' * by Delage and Herouard. 



It is usually stated that the flagellum arises either on the dorsal 

 wall of the gullet or from the protoplasm at its base. This, 

 however, is not correct. The flagellum not only does not ter- 

 minate in the gullet, but actually passes into the excretory 

 reservoir, with which, as I have shown, the gullet is in open 

 communication, and it becomes attached to its dorsal wall, or occa- 

 sionally to its ventral, by a bifurcate base (PI. 32. figs. 2 to 8). 

 This bifurcation extends as far as the anterior edge of the eye- 

 spot, at which point the single whip-like portion of the flagellum 

 begins (fig. 2). This mode of attachment of the flagellum has 

 not, so far as I am aware, been observed before ; it probably 

 serves to give it a much firmer support, and may be of mechanical 

 advantage to it in its movement. 



In addition to this bifurcation, we find another iuteresting 

 structure connected with the flagellum. On one of the branches 

 of the bifurcate base there occurs an oval swelling or enlargement, 

 immediately in front of the eye-spot, and just below the point 

 where the bifurcation begins (PI. 32. figs. 2, 8). It is in close 

 contact with the eye-spot when the cell is in the elongate motile 

 condition ; but it is not actually in organic connection with it, as 

 shown (PI. 32. figs. 7, 8), and in numerous cases which were 

 observed of Euglena-ceW^ in the resting condition, it was com- 

 pletely separated from it (fig. 9). In some cases, this enlarge- 

 ment appears in the position indicated in figs. 3 to 6, just above, 

 or at, the point of bifurcation of the flagellum ; but from a careful 

 examination of numerous specimens ia which this appearance 

 was seen, it seems to me that it is an eflect due to the second 

 branch of the bifurcation passing below the enlargement, and so 

 becoming hidden from view (compare figs. 7 and 8). 



Although both the bifurcation and the enlargement are visible 

 under favourable conditions, in the living cell, it is necessary in 

 order to see them clearly to resort to the use of reagents. The 

 best reagent for the purpose is a 1 per cent solution of osmic acid. 

 This kills motile Euglena-ceWs, at once, and leaves them in an 

 expanded condition with their flagella distinctly visible. They 

 should remain in this solution from three to forty-eight hours 

 or more, and may be examined in dilute glycerine. In order to 

 preserve them for future investigation, they may be kept in a 



* La Cellule et les Protozoaires, p. 305. 



