UNITY OF DESIGN. 635 



with a caudal prolongation of the sacrum, and 

 an intermaxillary bone ; and lastly, changing its 

 structure to one adapted to the erect position, 

 accompanied by a great expansion of the cerebral 

 hemispheres, which extend backwards so as 

 completely to cover the cerebellum. Thus does 

 the whole fabric arrive, by a gradual process of 

 mutation, at an extent of elaboration and refine- 

 ment, unattained by any other race of terrestrial 

 beings, and which has been justly regarded as 

 constituting the climax of organic develope- 

 ment.* 



It must, I think, be admitted that the analo- 

 gies, on which the hypothesis in question is 

 founded, are numerous and striking ; but great 

 care should be taken not to carry it farther than 

 the just interpretation of the facts themselves 



* A popular opinion has long prevailed, even among the 

 well informed, that mis-shapen or monstrous productions, or 

 lusus natures, as they were termed, exhibit but the freaks of 

 nature, who was believed, on these occasions, capriciously to 

 abandon her usual course, and to amuse herself in the production 

 of grotesque beings, without any special object. But it is now 

 found that all defective formations of this kind are occasioned 

 by the imperfect developement of some parts of the embryo, 

 while the natural process is carried on in the rest of the system ; 

 and thus it happens that a resemblance may often be traced, in 

 these malformations, with the type or the permanent condition 

 of some inferior animal. Hence all these apparent anomalies 

 are, in reality, in perfect harmony with the established laws of 

 organic developement, and afford, indeed, striking confirmations 

 ©f the truth of the theory here explained. 



