480 MR. HAKOLD WAGEE ON THE 



Summary. 



(1) The structure of the eye-spot in Euglena viridis, E. Ehren- 

 hergii, and PJtacus jpyriforme is not as Franze has described it. 

 The so-called "crystal body " and " lens bodies " were not found 

 in any of the individuals of the species examined by me. As 

 earlier observers have stated, the eye-spot consists simply of a 

 mass of pigment granules arranged in a single layer, and probably 

 embedded in a protoplasmic framework, but the latter could 

 not be seen, and its presence was only inferred from the fact 

 that the pigment granules must be held together in some way, 

 that the eye-spot as a whole is capable of expansion, and that the 

 pigment granules can be separated from each other. 



(2) The gullet at the anterior end of the body does not end 

 blindly, as was formerly supposed, near the principal vacuole, 

 but actually opens into it, thus forming one continuous cavity 

 open to the exterior. 



(3) The eye-spot is in close contact with the gullet at the 

 point where it opens into the excretory reservoir, and curves 

 around it slightly. 



(4) The flagellum is not attached to the wall of the gullet, 

 but arises from near the posterior or basal side of the excretory 

 reservoir, to which it is attached by a bifurcate base. The bifur- 

 cation begins at about the level of the eye-spot, and in this region 

 an enlargement of one of the basal supports takes place. This, 

 which is oval in shape, is in close contact with the eye-spot, on 

 its inner concave side. It is in the same position as that 

 described by Eranze for his " crystal body," and may have been 

 mistaken for this by him. 



(5) An explanation of this structure suggested by the author 

 is that the light which is absorbed by the eye-spot in some way 

 stimulates this enlargement, which in turn reacts upon the 

 flagellum and causes its movements to become modified. This is 

 supported by the facts which are stated in the three following 

 paragraphs. 



(6) The rays of light which are absorbed by the eye-spot — 

 those in the region of the blue of the spectrum — are the same as 

 those which are active in modifying the direction of movement 

 of the Euglena-ceW. 



(7) These rays can only influence the movements of the cell 

 by acting upon 'or controlling in some way the mechanism by 

 which the flagellum moves. 



