10 



VEGETABLE PHYSIOLOGY. [LESSON 3. 



suddenly contracts in bulk, and seeks the centre of the cell, then it 

 spontaneously divides (a, a), at the same time a delicate line is run, 

 as it were, across the cell dividing it into two immediately beneath 

 the divided endochrome (b). 



56. Subsequently, the divided endochrome seeks the centre of 

 each cell, the spiral coil is broken up, and the entire mass assumes 



FIG. 8. FIG. 9. 



Zygnema (Frog's spittle) in the Development of Zygnema, Spontaneous division (third 

 first stage. progressing (second stage). stage). 



the solid cylindrical form which characterized the first figure of this 

 series ; the cells become well formed, and grow correspondingly with 

 the increased size of the endochrome, and especially of its nuclei 

 the whole cell, in fact, is preparing to go through the like series of 

 consecutive changes, in which it originated. 



57. Again, as regards the vegetative type of the original con- 

 stitution of animal tissues, we find among the lowest tribes of 

 animals, as well as among certain of the highest tribes that retain 

 many embryonic peculiarities, even in the adult condition, a great 

 proportion of the complete fabric to be possessed of a distinct vege- 

 tative origin. In most of the higher animals, however, a large pro- 

 portion of the structure consists of tissues in which no distinct trace 

 of a cellular origin appears to be apparent ; and it has been only 

 since improved methods of observation have been brought to bear 

 upon their analysis, and more especially since they have been exam- 

 ined not only in their complete state, but in the course of their de- 

 velopment, that they have been reduced to the same category with 

 the tissues of plants, and of the lower animals. 



