36 COCCOPHYCE. 
to end in such a way as to form polygonal and mostly pentagonal 
meshes, the size of which varies with the age of the plant. These cells, 
which are closely conjoined, but have no passage-ways between them, 
are capable of independent life, so that the Hydrodictyon may be looked 
upon as an elaborate type of a cell-family, one in which cells are con- 
joined in accordance with a definite plan, so as to make a body of definite 
shape and size, yet in which each cell is an independent being, drawing 
nothing from its neighbours. The cells themselves are cylindrical, with 
a thickish cellulose wall, and having no nuclei. Their chlorophyllous 
protoplasm is granular, and is placed in the exterior portion of the cell, 
forming thus, within the outer wall, a hollow cylinder, in which are im- 
bedded starch granules, and whose interior is occupied with watery 
contents. The Hydrodictyon cell, when once formed, is capable of growth. 
but not of going through the usual process of cell multiplication by 
division, so that the adult frond is composed of just as many and, in- 
deed, the same cells as it had inits earliest infancy. 
“No trae sexual reproduction has as yet been discovered in the water- 
nets. There have been described, however, two forms or methods in 
which the species multiplies, both of them occurring by means of motile 
zoosporoid bodies. In the one case these develop immediately into the 
new plant, whilst in the other, before doing so, they pass through a 
resting stage. Of the life history of the latter, the microgonidia, I 
have no personal knowledge. 
“The investigation of the production and development of the macro- 
gonidia, however, has occupied considerable of the time devoted by 
myself to the microscope, and I have seen large numbers of specimens 
in almost all the stages of development. I have never been able to 
detect any decided motion in the macroyonidia. 
“They are formed in the protoplasmic stratum already alluded to as 
occupying the outer portion of the interior of the Hydrodictyon cell. 
The first alteration in this, presaging their formation, is a disappearance 
of the starch granules, and a loss of the beautiful transparent green 
colour. Shortly after this, even before all traces of the starch-grain 
are gone, there appear in the protoplasm numerous bright spots placed at 
regular intervals; these are the centres of development, around which 
the new bodies are to form. As the process goes on, the chlorophyl 
granules draw more and more closely around these points, and at the 
same time the mass becomes more and more opaque, dull, and yellowish 
brown in colour. This condensation continues until at last the little 
masses are resolved into dark hexagonal or polygonal plates, distinctly 
separated by light, sharply defined lines. In some the original bright 
central spot is still perceptible, but in others it is entirely obscured by 
the dark chlorophyl. The separation of these plates now becomes more 
and more positive, and they begin to become convex, then lenticular, 
and are at last converted into free, oval, or globular bodies. When 
these are fally formed they are said to exhibit a peculiar trembling 
motion, mutually crowding and pushing one another, compared by A. 
Braun to the restless, uneasy movement seen in a dense crowd of 
people in which no one is*able to leave his place. Whilst the process 
jast described has been going on, the outer cellulose wall of the Hydro- 
dictyon cell has been undergoing changes, becoming thicker and softer 
and more and more capable of solution, and by the time the gonidia 
are formed it is enlarged and cracked, so that the room is afforded 
them to separate a little distance from one another within the parent- 
cell. Now the movements are said to become more active—a trembling 
jerking which has been compared to the ebullition of boiling water. 
There is, however, with this a very slight change of space, and in a very 
short time the gonidia arrange themselves so as to form a little net 
within the parent-cell, « miniature in all important particulars of the 
