26 report— 1879. 



of the nature and properties of one special modification of matter, which 

 will yield to none other in the interest which attaches to its study, and in 

 the importance of the part allocated to it in the economy of nature. Did 

 the occasion permit I might have entered into many details which I have 

 left untouched ; but enough has been said to convince you that in proto- 

 plasm we find the only form of matter in which life can manifest itself ; 

 and that, though the outer conditions of life — heat, air, water, food — 

 may all be present, protoplasm would still be needed, in order that these 

 conditions may be utilised, in order that the energy of lifeless nature may 

 be converted into that of the countless multitudes of animal and vege- 

 table forms which dwell upon the surface of the earth or people the 

 great depths of its seas. 



We are thus led to the conception of an essential unity in the two 

 great kingdoms of organic Nature — a structural unity, in the fact that 

 every living being has protoplasm as the essential matter of every living 

 element of its structure ; and a physiological unity, in the universal 

 attribute of irritability which has its seat in this same protoplasm, and is 

 the prime mover of every phenomenon of life. 



We have seen how little mere form has to do with the essential 

 properties of protoplasm. This may shape itself into cells, and the cells 

 may combine into organs in ever-increasing complexity, and protoplasm 

 force may be thus intensified, and, by the mechanism of organisation, 

 turned to the best possible account ; but we must still go back to pro- 

 toplasm as a naked formless plasma if we would find — freed from all 

 non-essential complications — the agent to which has been assigned the 

 duty of building up structure and of transforming the energy of lifeless 

 matter into that of living. 



To suppose, however, that all protoplasm is identical where no 

 difference cognisable by any means at our disposal can be detected would 

 be an error. Of two particles of protoplasm, between which we may 

 defy all the power of the microscope, all the resources of the laboratory, 

 to detect a difference, one can develope only to a jelly-fish, the other only 

 to a man, and one conclusion alone is here possible- — that deep within 

 them there must be a fundamental difference which thus determines their 

 inevitable destiny, but of which we know nothing, and can assert nothing 

 beyond the statement that it must depend on their hidden molecular 

 constitution. 



In the molecular condition of protoplasm there is probably as much 

 complexity as in the disposition of organs in the most highly differentiated 

 organisms ; and between two masses of protoplasm indistinguishable from 

 one another there may be as much molecular difference as there is between 

 the form and arrangement of organs in the most widely separated animals 

 or plants. 



Herein lies the many-sidedness of protoplasm ; herein lies its sig- 

 nificance as the basis of all morphological expression, as the agent of 



