INTRODUCTION. 9 



shortly afterwards cell-nuclei, and subsequently also cells were 

 found in all tissues of the animal body at their origin ; so that 

 all tissues consist of cells, or are formed by various modes, from 

 cells. The other proof of the analogy between animal and vege- 

 table cells was thus afforded. 



I shall follow the same course in communicating the separate 

 observations, and shall speak, therefore, in the next place of the 

 structure and growth of the chorda dorsalis and cartilage, and 

 in the second section treat of the germinal membrane and the 

 remaining tissues. 



