Conklin.j ^^ [May 1, 



that they are always associated with more or less complex structures; 

 in fact, that they are dependent upon structure. 



The smallest and simplest mass of protoplasm that can manifest all 

 the fundamental phenomena of life, such as assimilation, growth, 

 division, and metabolism, is an entire cell, nucleus and cytoplasm, 

 and probably centrosome. The cell is composed, as microscopic study 

 plainly reveals, of many dissimilar but perfectly coadapted parts, each 

 performing its specific function, and it may therefore properlj' be called 

 an organism. Some phenomena of cell life may be directly referred to 

 the various visible constituents of the cell, but many of them are evi- 

 dently connected with structures ivhich we cannot see, structures 

 which may perhaps never be seen, and yet which must be vastly more 

 complex than the most complex molecules known to chemistry, and 

 yet much more simple than the microsomes, centrosomes, and chromo- 

 somes which are visible in the cell. With these ultra-microscopical 

 particles many of the most fundamental phenomena of life are asso- 

 ciated, viz., assimilation, growth, metabolism, and probably differentia- 

 tion, repetition, and variation. These functions are so coordinated that 

 there can be no question that the ultra-microscopical structure is an 

 organization, with part coadapted to part. The organization of the 

 cell, therefore, does not stop with what the microscope reveals, but 

 must be supposed to extend to the smallest ultimate particles of living 

 Blatter which manifest specific functions. These are the vital units so 

 generally postulated, the "smallest parts" of living matter, as they 

 were called by Briicke, who first demonstrated that they must exist \. 

 the "physiological units" of Spencer, the "gemmules" of Darwin, 

 the "micella-groups" of Nageli, the "pangenes" of De Yries, the 

 "plasomes" of Wiesner, the "idioblasts" of Hertwig, the "bio- 

 phores " of Weismann. Such ultimate units have been found abso- 

 lutely necessary to explain those most fundamental of all vital phe- 

 nomena, assimilation and growth, while many other phenomena, espe- 

 cially particulate inheritance, the independent variability of parts, and the 

 hereditary transmission of latent and patent characters, can at present 

 only be explained by referring them to ultra-microscopical units of 

 structure. To deny that there are such units does not simplify the 

 problem, as some seem to suppose, but renders it impossible of^ip- 

 proach. A corpuscular hypothesis of life, like that of light, may be 

 only a temporary makeshift, but it is better than nothing. 



Whitman* well says : "Briicke's great merit consists in this that he 

 taught us the necessity of assuming structure as the liasis of vital phe- 

 nomena, in spite of the negative testimony of our imperfect micro- 

 scopes. That function presupposes structure is now an accepted axiom, 

 and we need^only extend Briicke's method of reasoning, from the tissue 

 cell to the egg cell, in order to see that tliere is no escajK' from the 



* C. O. Whitmun, The Inadequacy of the CcU-Theonj of Dcvclvpiiunt, Biological Lectures, 

 1893. 



