22 SATUJIDAY LKCTUIJKS. 



the posterior limbs of ordinary quadrupeds, the legs of the 

 human subject, the hind flippers of seals, and the caudal or 

 tail fin of the whale are homologous. Several of the bones 

 of the suspensorium of the lower jaw of the fishes and the 

 ear bones of man are also homologous, although, be it re- 

 membered, they have no functions corresponding, being in 

 that respect entirely dissimilar. Yet, again, homology is 

 seen in the air-bladder of the fish and lungs of mammals ; 

 and, further, in the gills and branchiostegal bones of fish 

 and the hyoid apparatus of man and other mammals. In 

 all cases their functions are very dissimilar. 



But do not infer that there is any necessary contrast be- 

 tween analogy and homology. Of course those parts which 

 are formed of the same elements, and have the same func- 

 tions, are both homologous and analogous. 



It is by a strict attention to the principles thus expressed 

 that natural history has attained its present high state, and 

 we may, therefore be pardoned for believing that the tree of 

 biological knowledge which has grown to its present height, 

 and which is attaining maturity by attention to such meas- 

 ures is justified by its fruits. 



But as the hour which we agreed to devote to our sub- 

 ject has been considerably exceeded, I shall not detain you 

 longer, but, with thanks for your attention, retire from the 

 platform. 



