from the Cell-contents of the Characeae. 109 



The production of the young Water-net, or Hydrodictyon, is 

 not unlike this. Here a single gonidiuni grows into a long 

 tubulur cell, during which its internal surface becomes lined 

 with a mucus-layer charged with chlorophyll-granules and 

 starch-grains; this layer, when fully dcv(l()i)ed, divides up into 

 gonidia, which, by mere change of position (liraun), force them- 

 selves into a new Water-net, or separate altogether, and pass out 

 through a rent in the parent gonidiuni, now become a long 

 cylindrical cell ; at this moment also the existence of another 

 more delicate cell, between the outer one and the mucus-layer, 

 is demonstrated, in which the passage of the gonidia is mo- 

 mentarily arrested. Here, then, the chief apparent difference 

 between this process of development or multiplication and that 

 of the globular cell of the mucus-layer of Sitella is the intro- 

 duction of foreign material for the support of the mass during 

 the time it is undergoing division in the latter, and the prepara- 

 tion of it in the cell itself for this process in the former. Here 

 also the cell-wall of the gonidiuni passes into the cell-wall of the 

 mother-cell in Hydrodictyon, which corresponds to the so-called 

 " gonidial cell " of Nitella, and is not a new secretion ; while 

 the internal delicate membrane which holds the gonidia in 

 Hydrodictyon corresponds to the delicate cell-membrane which 

 inmiediately surrounds the monads in Nitella ; and the monads, 

 as well as the gonidia of Hydrodictyon, appear to gain their 

 proper covering from the contents of the secondary cysts, which 

 coverings in time become respectively the mother-sacs of future 

 litters. We shall also see by and by, that the same thing takes 

 place in the segmentation of Paraniecia. 



The passage of the green disks m situ into monads or poly- 

 morphic cells, mentioned p. 8, is now easily understood; since, 

 if the germ producing the first globular vesicle can get through 

 the cell-wall of the internode without causing a suspension of its 

 functions, a germ from it might easily get from the mucus-layer 

 into the green disk of the green layer; and there, living upon 

 tiie protein nucleus and green chlorophyll, take the place of the 

 latter in the transparent cell, which, finally decaying, would 

 allow the monad or monads thus produced to get into tlie cavity 

 of the internode. 



Viewing, then, the globular vesicles as an infusorial develop- 

 ment, all difficulty in accounting for the changes which they 

 occasion in the cells of the Characece disappears, and all changes 

 which take place in these vesicles themselves become easily 

 understood. 



But we have yet to discover whether these vesicles existed ah 

 origine in the mucus of the internode, and, if not, how and under 

 what form they were introduced. 



