34 STRUCTURE AND GROWTH 



remains of the cell- cavities also become filled with it at a 

 subsequent period, and at the same time the stellated canali- 

 culi issuing from them make their appearance. The formation 

 of these canaliculi probably takes place by the transformation 

 of round cartilage-cells into a stellated form, after the manner 

 of the pigment-cells at plate II, figs. 8 and 9. 



The above detailed investigation of the chorda dorsalis and 

 cartilage, has conducted us to this result, — that the most impor- 

 tant phenomena of their structure and development accord with 

 corresponding processes in plants, that some anomalies and 

 differences may indeed still remain unexplained, but that 

 they are not of sufficient importance to disturb the main con- 

 clusion, viz. that these tissues originate from cells, which 

 must be considered to correspond in every respect to the 

 elementary cells of vegetables. Thus then are we furnished 

 with the first of the proofs required in the Introduction ; that 

 is to say, we have shown with regard to a certain tissue, that 

 it not only originates from cells, but that these cells in the I 

 process of their development manifest phenomena analogous to 

 those of the cells of plants. We have now thrown down a 

 grand barrier of separation between the animal and vegetable 

 kingdoms, viz. diversity of structure. We have become ac- 

 quainted with the signification of the individual parts of the ani- 

 mal tissues as compared with the vegetable cells, and know that 

 cells, cell-membrane, cell-contents, nuclei, and nucleoli in the 

 former are in every respect analogous to the parts having 

 similar names in the cells of plants. We have already observed 

 several modifications both of the nucleus and cell. The former 

 presented itself as a corpuscle having either an oval or circular 

 outline, spherical in figure, or very much flattened, sometimes 

 hollow, and often scarcely perceptible, in consequence of its 

 transparency, but generally granulous and yellowish, and con- 

 taining in its interior from one to three nucleoli. This 

 nucleus lay within, and fast adhering to the w* all of the cell, 

 but never in its centre. The fundamental form of the cell 

 appeared to be that of a round vesicle, but we have also ob- j 

 served the flattening of the cells against one another, the 

 presence of intercellular substance between them in greater 

 or less quantity, and lastly, the thickening of the cell-walls. 



