234 Thomas H. Huxley, Esq., on the 



Reflecting on the fact, that iodine has been detected in all 

 the trials I have hitherto made on sea-fish, it seemed proba- 

 ble that guano, considering its origin, would not be destitute 

 of this substance ; and the result of experiments has been 

 confirmatory ; using the test-method noticed above, a distinct 

 indication of its presence was obtained, both in the instance 

 of the Peruvian and African guano, the only two I have yet 

 tried. 



Lesketh liow, June 1, 1853. 



On the Identity of Structure of Plants and Animals. By 

 Thomas H. Huxley, Esq., F.R.S. Read before the Royal 

 Institution. 



The lecturer commenced by referring to his endeavours 

 last year to shew that the distinction between living creatures 

 and those which do not live, consists in the fact, that while 

 the latter tend to remain as they are, unless the operation 

 of some external cause effect a change in their condition, the 

 former have no such inertia, but pass spontaneously through 

 a definite succession of states — different in kind and order of 

 succession for different species, but always identical in the 

 members of the same species. 



There is however another character of living bodies, Or- 

 ganization — which is usually supposed to be their most strik- 

 ing peculiarity, as contrasted with beings which do not live ; 

 and it was to the essential nature of organization that the 

 lecturer on the present occasion desired to direct attention. 



An organized body, does not necessarily possess organs in 

 the physiological sense — parts, that is, which discharge some 

 function necessary to the maintenance of the whole. Neither 

 the germ nor the lowest animals and plants possess organs 

 in this sense, and yet they are organized. 



It is not mere external form, again, which constitutes or- 

 ganization. On the table there was a lead-tree (as it is called), 

 which, a mere product of crystallization, possessed the com- 

 plicated and graceful form of a delicate fern. If a section 



