94 INDEPENDENT CELLS UNITED 
thus an uninterrupted passage from one cell-cavity into the 
other is produced. I am not certain as to whether a similar 
process does not take place in some fibres of the crystalline 
lens. 
The transformations which the cells undergo are not, how- 
ever, restricted to those already mentioned. A completely 
opposite process occurs in the cortical substance of the shaft 
of feathers, viz. a division of the cells into fibres. By this 
process, out of a single celi several fibres are generated, which, 
in the first instance, are united together by the rest of the 
substance of the cell, but at a later period of development may 
be insulated to a considerable extent. An elongation of the 
cells into these fibres takes place, indeed, at the same time, 
but the major portion of each fibre is formed by the division 
of the bodies of the cells. 
With respect to the formation of the cells of this class, we 
find it to be a constant rule, that their size increases in pro- 
portion with their age, a fact which Henle has already pointed 
out with. regard to the epithelium. We have seen in the dif- 
ferent tissues, that the nucleus is first present, that the cell is 
then formed around it, the nucleus, therefore, being the true 
cytoblast, and that it holds the same position in these cells 
that it does in those of plants, being fixed eccentrically upon the 
internal surface of the wall. Cell and nucleus advance in 
growth for a time, the former, however, much more vigorously 
than the latter. The nucleus is generally absorbed after the 
formation of the cell is completed. The generation and growth 
of the cells and all the phenomena connected with the nucleus 
resemble those of the vegetable cells, and we may unhesi- 
tatingly draw a parallel between them. In no class is the 
quantity of the cytobiastema smaller than in this. In the 
immature state the walls of the cells lie close together, with 
at the most, but a minimum of intercellular, substance be- 
tween them at points where three cells are in contact, and it 
is only between those nuclei, around which no cells have as yet 
formed, that a somewhat larger quantity of cytoblastema is 
present. . 
The class of cells now treated of, and the teeth which will 
be examined in the following class, have been comprised under 
the term unorganized tissues, and their growth represented as 
