THE BEGINNINGS OF LIFE. 229 



have nearly attained their full size, are still (although 

 units exhibiting a distinct vitality of their own) mere 

 structureless bits of protoplasm, without cell-wall and 

 without nucleus differing, in fact, in no respect from 

 the Protamvtyj' of Professor Haeckel, except that they 

 are subordinate parts of a higher organism, and there- 

 fore do not lead an entirely independent existence. 

 It seems evident also that such homogeneous masses 

 of matter (plastides), already exhibiting vital character- 

 istics, are afterwards capable of evolving a nucleus, and 

 of assuming that cellular form without which it was 

 formerly supposed no vital manifestations could occur. 



Such a mode of origination of living units, together 

 with their subsequent evolution, affords perhaps the 

 best illustration that can be given of the birth of 

 cells de novo in blastemata. Other evidence of vari- 

 ous kinds can however be adduced tending towards 

 the same conclusion, and to this we will now briefly 

 allude. When working at the anatomy of a diseased 

 spinal cord in the year 1866, before my faith in 

 Virchow's doctrines had been notably shaken, I was 

 much struck by certain appearances met with through- 

 out the degenerated portions of a cord in which the 

 interstitial fibrous tissue had become abnormally in- 

 creased in quantity. As in such tissue generally, there 

 was a very great increase in the number of nuclei, and 

 although very many of them appeared about ;30 ' 00 " in 

 diameter, there were others even larger than this, and 

 others still in great abundance representing every 



