470 ME. HAEOLD WA&EE ON THE 



figures would indicate), and to the fact that it is curved around 

 the gullet and is sometimes sharply turned in here and there at 

 the edge. The eye-spot has thus not only aa irregular contour, 

 but its surface is very uneven, and under a low power with poor 

 definition it may sometimes present an appearance of colourless 

 granules embedded in the pigment. Under a high magnifying- 

 power with good definition, this appearance vanishes completely, 

 and the eye-spot is resolved into the simple granular structure 

 to which reference has already been made. 



The pigment granules are brightly refractive and have a very 

 distinct outline. They form a single layer, and in Euglena 

 viridis are easily separated from each other, especially when 

 the cells are in the enycsted condition. In some eye-spots the 

 granules are spherical and all of the same size, but in others they 

 are more irregular in shape and of difi'erent sizes, and in such cases 

 the eye-spot is more homogeneous in appearance, especially near 

 the middle. 



By the action of strong potash solution the eye-spot swells up, 

 and the pigment granules become separated from one another *. 

 The arrangement of the granules is not very definite, but now and 

 then they were found to be grouped in rows, sometimes radiating 

 from the centre (fig. 1, a). The number of granules present 

 varies, but not to any great extent : in a fairly large number of 

 cases which I counted, I found that between 30 and 40 granules 

 were the most frequent. If the action of the potash is continued 

 for some time, the eye-spot disintegrates more or less completely 

 into a number of granules (PI. 32. fig. 1, d). Even in the living 

 condition, the eye-spot sometimes breaks up into a number of 

 separate granules which become distributed through the proto- 

 plasm. This is frequently found to be the case in cells which 

 have become encysted and surrounded by a thick wall. I have 

 never seen it in elongate motile cells, although I have often 

 noticed in the surrounding protoplasm a number of granules of 

 the same size and colour as those in the eye-spot, and looking as 

 if they had been separated from it. They can be easily dis- 

 tinguished from the rusty-red granules, which appear in the 

 protoplasm as a result of the disintegration of the chlorophyll 

 grains, by their bright red or orange colour and greater refractive 

 power. The nature of this colouring-matter has not been fully 



* Klebs, I. c. 



