NATURAL HISTORY. 19 



rendered useless when separated. If all these parts had not been made 

 distinct, but had been blended through the whole animal, so that every 

 part formed a compound of the whole, e. g., if every part formed bile, 

 every part formed urine and secreted seed, &c, then each part of an 

 animal would become a whole ; so that, when any part was removed, 

 it might be considered as a perfect animal. This is, in fact, the case 

 with many animals 1 , but in other respects they are different from vege- 

 tables. 



As most animals have parts allotted for every purpose, [each] to 

 answer its purpose and no other, the testicles and ovaria then answer the 

 purpose of generation and no other purpose. They are parts whose actions 

 are independent of all other parts of the body ; only [they are] obliged to 

 the circulation for supplies, and to the nerves for powers of action. But 

 their particular actions depend upon themselves ; therefore, the testicles 

 and ovaria produce tbe distinct species independent of the whole. 



To illustrate this with a supposed experiment : let us take a testicle 

 from a cock and put it into the belly of a gander. If it was possible 

 that the ducts could unite so as to carry the seed that was secreted in 

 that testicle to the female, the produce would be the same as if a cock 

 had trod a goose ; so that the powers of the testicle would remain the 

 same as if they had never been transplanted, and would continue to 

 secrete the same kind of semen. The inclinations of the gander would 

 not be towards the hen but towards a goose ; for, although the testicles 

 are the cause of the inclination, yet they do not direct these inclina- 

 tions : these inclinations become an operation of the mind, after the 

 mind is once stimulated by the testicle. 



Vegetable and animal life are very similar. They are both capable 

 of being engrafted by parts that are similar to themselves. Whether 

 an animal could be engrafted upon a vegetable, or a vegetable upon an 

 animal part, is not yet known 2 . 



Similarity in the Propagation of the Species between some Animals 

 and some Vegetables. 



Vegetables are not only similar to all animals in the circumstance of 

 simple life, but are similar, in the propagation of their species, to some 



1 [The infusory and other Protozoa ; the hydra polype and other Hydrozoa, &c. 

 Hunter's previous propositions will be understood to refer to the more conspicuous 

 and higher animals, constituting the ordinary idea of the class.] 



2 [The parasitic growth of certain cryptogamic plants (e. g. Sph&ria) in and upon 

 the larvae of certain insects, giving rise to the combination called in New Zealand 

 the ' tree-caterpillar,' would be, perhaps, the nearest known illustration of Hunter's 

 idea] 



C 2 



