202 THE PHENOMENON OF 



mucilaginous layer. These spots are not the starch-grains 

 undergoing solution, as might be conjectured, for their 

 number is much larger than that of the latter, the not 

 quite lost nuclei of which may still be remarked here 

 and there, and not in, but between the spots. The little 

 green granules of the contents, which, for the sake of 

 brevity, I shall call chlorophyll-granules,* do not disap- 

 pear with the starch-grains, but separate from each other 

 at the period of the formation of the spots, and become 

 accumulated as darker boundary lines between the 

 brighter spots. By adjusting the focus up and down we 

 may ascertain that scattered chlorophyll-granules occur 

 also above and beneath the light spots, while the spots 

 themselves are roundish spaces, free from granules, 

 existing in the thickness of the mucilaginous layer. 

 Simultaneously with these processes the green colour of 

 the mucilaginous layer passes more into a brownish, 

 a change of colour which shows itself still more clearly 

 in the next stage, especially in those cells in which 

 microgonidia (swarmers) are to be formed. Still more 

 striking alterations present themselves in the second stage 

 of the formation of gonidia, in which the mucilaginous 

 layer exhibits a picture diametrically opposed to that just 

 described. The granules retreating towards the bright 

 spaces, the earlier dark net-work of the granules is 

 replaced by a net-work of lighter boundary lines; the 

 former bright spots, on the contrary, become darker areolae 

 through the collection of granules into groups. When the 

 new distribution of the contents is complete, the light inter- 

 mediate streaks appear as everywhere pretty equally broad, 

 light-yellowish (not green) lines, sharply defined upon the 

 dark field ; the latter displays little polygonal (mostly hex- 

 agonal, rarely pentagonal or heptagonal) green plates, with 



* These granules are not chlorophyll-vesicles, as in Taucheria, Chara, &c., 

 they have more the aspect of dense, mostly lougish granules, without any 

 enveloping membrane. When the chlorophyll is extracted by spirits of 

 wiue, these, like the remainder of the contents, become bleached, but remain 

 distinguishable ; the shape, however, becomes irregular through the action of 

 the spirit. 



