VITAL FORCE, IXSTINXT, AND SENSATION. 51 



of its own of a certain specific constitution. And, further, we must assume that 

 this specific protoplasmic constitution is transmitted from one generation to anotlier, 

 so that the pi-otoplasm of the oleander, for example, had exactly the same constitu- 

 tion thousands of years ago as it has to-day. Lastly, we must assume that each 

 special kind of protoplasm has the power to reproduce its like, ever anew, from 

 the raw materials occurrino- in its envii-oument. 



VITAL FOECE, INSTINCT, AND SENSATION. 



The phenomena observed in living protoplasm, as it grows and takes definite 

 form, cannot in their entirety be explained by the assumption of a specific con- 

 stitution of protoplasm for every distinct kind of plant; though this hypothesis 

 will again prove very useful when we inquire into the origin of new species. 

 What it does not account for is the appropriate manner in which various functions 

 are distributed amongst the protoplasts of a cell-connnunity; nor does it explain 

 the purposeful sequence of difl'erent operations in the same protoplasm without 

 any change in the external stimuli, the thorough use made of external advan- 

 tages, the resistance to injurious influences, the avoidance or encompassing of 

 insuperable obstacles, the punctuality with which all the functions are performed, 

 the periodicity which occurs with the greatest regularity under constant condi- 

 tions of the environment, nor, above all, the. fact that the power of discharging 

 all the operations requisite for growth, nutrition, renovation, and multiplication 

 is liable to be lost. We c;Ul the loss of this power the death of the protoplasm. 

 It ensues upon assaults from without if they succeed in destroying the molecular 

 structure so entirely as to render reconstruction impossible; but, furthermore, 

 ileath may take place without external cause. 



If cells of the blood-red alga, previously mentioned as allied to the red-snow, 

 are collected from hollows in stones, casually full of rain-water, and are kept 

 dry for weeks and then again moistened, the water is found to have a very power- 

 ful eflect. The protoplasm becomes mobile, and swarm-spores are formed which 

 put forth viliratile cilia, propel themselves about for a short time in the water, 

 and then settle down in some favoured spot, draw in their cilia, come to rest 

 and ilivide, producing otf'spring which again are motile. This alga may be kept 

 dry for months, nay even over a year, and still its cells exhibit the movements 

 above described when put into water. But if a mass of it is preserved under 

 these same conditions for many years and then moistened, the little cells will, it 

 is true, take up additional water, but motile cells are no longer formed. The 

 cells do not move, nor grow, nor divide, but gradually become discoloured; are first 

 disintegrated and then dissolved. We say then that in them life could no longer 

 lie recalled, and we describe them as dead. 



The same thing is observed in great cell-communities. The seeds of manj' species 

 1 if plants preserve the capacity for germination for an incredibly long period, especially 

 \vhen kept in a dry place. If after ten years such seeds are transferred into 



