172 THE PHENOMENON OV 



and indeed swell up more strongly than the outer layers, 

 thus often falling into wave-like folds. The layers of the 

 cell-membrane do not exhibit the slightest trace of punc- 

 tation, or of a composition from globules ; they are 

 always homogeneous and hyaline. 



2. The outer mucilaginous layer. This is thicker than 

 the primordial membrane, but far thinner than the inner 

 mucilaginous layer. When separated from the primordial 

 membrane, its outer surface appears rough and wavy, as 

 also its inner surface, which is connected here and there 

 with the inner mucilaginous layer by stretched mucila- 

 ginous threads, and hence often appears torn on the 

 inside. It is also opakish, of a yellowish colour, and 

 exhibits largish, irregular, and indistinctly defined muci- 

 lage-granules. 



3. The inner mucilaginous layer. This is the thickest 

 of the three layers, rough on the outside, wavy, and 

 exhibiting large, strong projections on the inside, de- 

 pending on the starch- vesicles occurring in it. Only this 

 layer is green, and, indeed, in vigorous and healthy cells, 

 of a continuous green colour, strewn over besides with 

 innumerable, mostly rather largish, dark-green granules, 

 about T^gth of a millimet. long, which sometimes form 

 interrupted, curved, and much intertwined rows, but more 

 frequently appear uniformly scattered. These granules 

 are not yet distinguishable in young cells. This layer 

 also contains the starch vesicles, which appear as bright 

 globules, of at most T ^th of a millim. thickness. Their 

 number increases with the age of the cell; while the 

 young cell, in the first day of the formation of the net, 

 possesses only a single starch vesicle, on the second at 

 most 2, on the third 3 '5, on the fourth 5 10, vesicles, 

 the full-grown cell, about three weeks old, displays 

 several thousands of them, which give the Water-net a 

 beautifully punctated appearance,* and were wrongly 



* Vaucher, 'Histoire des Conferves d'Eau douce,' 1803, described the 

 starch vesicles as grains brillans, and considered them the male organs of 

 Hydrodictyon. 



