38 PROTOPLASMIC THEORY BEFORE 1860. 



has frequently disappeared before the metamorphosis begins, 

 but of intimate molecular changes in its substance." 



In this section we perceive that, side by side with the de- 

 velopment and modification of the cellular theory, has been 

 growing up the recognition of the fact that in the sarcode of 

 animals, and the protoplasm of plants, we see the simplest 

 and probably ultimate form of living matter. Those who are 

 guided by the light of Fletcher's hypothesis are no doubt pre- 

 pared to see in this the realization of his one and only irritable 

 or living matter. But that any such impression was general, or, 

 indeed, had a place at all among physiologists, even in 1853. 

 the above testimony of Huxley is sufficiently significant in the 

 negative. 



In the foregoing resume I have purposely confined 

 myself to works written before I860, and given chiefly 

 an analysis of a few of the chief memoirs on the sub- 

 ject, with little comment, in order that the meaning 

 may emerge unbiassed by observations made in the 

 light of subsequent knowledge, which is seldom the 

 case with compendious treatises. From this it appears 

 that the threefold form of the cell was soon given up, 

 and that, although the dual form of the nucleated cell, 

 without cell wall, nominally holds its place still, life 

 has been shown to exist in the simple form of a 

 structureless, viscid, semifluid matter common to both 

 animals and plants. The bearing of this on the local- 

 ization of the living matter in the complete indi- 

 viduals of the higher orders appears as yet not to have 

 been thought of, and almost the whole reference of 

 these facts has been made to development alone. And, 

 in fact, Schwann's and Schleiden's chief aim was to 

 demonstrate the existence of a " common principle of 

 development for all the elementary parts of the organ- 



