112 Mr. H. J. Carter on the Development of Gonidia 



Thus we see that the mucus-layer appears originally to be 

 formed by cells of extreme tenuity, and that even the first cell 

 which presents a circulation may have the irregular, agariciform 

 bodies in it. 



Now the same thing takes place in the roots (fig. 37), which 

 are given off in a circlet from the first internode or junction of 

 the first cell with the cavity of the nucule (fig. 35 e), and at this 

 period far exceed the plant in length and amount of development. 

 They however present these exceptions, viz. that they are as trans- 

 parent as glass, from having no green disks, and for some time 

 bear a large cytoblast in their extremity (/), which however, as 

 the root elongates, adheres to one side (g), and there appears to 

 undergo fissiparation and throw out a new circlet of roots {h), 

 while the old root ends some distance beyond this in a cul de sac 

 without further development. 



Thus we have the green cells of the plant at first, as well as 

 the roots, so transparent, that the delicate hyaline vesicles which 

 precede the formation of the mucus-layer can be distinctly seen 

 through them ; while afterwards, when the mucus is fully formed 

 and in circulation in both, and an equal degree of transparency 

 still remains in either, no vesicles whatever can be seen, nor 

 anything like the nuclei belonging to the "globular vesicles;^' 

 though, as before stated, a variable number of the irregular 

 bodies may already be present. 



Hence we may fairly infer two things, viz. first, that the 

 globular vesicles at least do not exist ab origine in the mucus- 

 layer; and, secondly, that the irregular-shaped or agariciform 

 bodies may be formed in it independently of the presence of the 

 globular vesicles. 



As to the external source of the globular vesicles, it does not 

 seem improbable, now that we know them to be so like Rhizo- 

 poda in almost every respect, and to produce monads which pass 

 into small amoebous cells, that they should originally come from 

 germs of their family ; particularly as all the freshwater species 

 dwell upon the freshwater Algse, are chiefly dependent on the 

 mucus of their cells for food, and are always found in greater or 

 lesser numbers creeping over their tender shoots, or present at 

 the formation of the resting-spores, when the cell-membrane is 

 so soft that it can be most easily penetrated. 



If we saw an Arcella or Diffiugia developed from one of these 

 monads which pass into an amoebous form, we should have no 

 doubt about the matter; nor ought we to have much, I think, if 

 we can find one Alga developing itself in another under similar 

 circumstances. 



For instance, we will take (Edogonium germinating in the midst 

 of the living cells of a filament of Oscillatoria {princeps, Kg.). 



