ORGANIC DEVELOPEMENT. 553 



always been great difficulty in understanding how 

 they obtain the nourishment so provided. A recent 

 discovery of Geoffroy St. Hilaire appears to have 

 resolved the mystery with respect to the Delp/iinus 

 globiceps, for he found that the mammary glands 

 of that animal contain each a large reservoir, in 

 which milk is accumulated, and which the dolphin 

 is capable, by the action of the surrounding mus- 

 cles, of emptying at once into the mouth of its 

 young, without requiring from the latter any effort 

 of suction.* 



The rapid sketch which I have attempted to 

 draw of the more remarkable steps of the early 

 stages of organic developement in the higher ani- 

 mals, taken in conjunction with the facts already 

 adverted to in various parts of this Treatise, and 

 particularly those relating to ossification, dentition, 

 the formation of hair, of the quills of the porcupine, 

 of the antlers of the stag, and of the feathers of 

 birds, will suffice to show that they are regulated 

 by laws which are definite, and preordained ac- 

 cording to the most enlarged and profound views 

 of the future circumstances and wants of the ani- 

 mal. The double origin of all the parts of the 

 frame, even those which appear as single organs, 

 and the order of their formation, which, in each 

 system, commences with the parts most remote 

 from the centre, and proceeds inwards, or towards 

 the mesial plane, are among the most singular and 

 unexpected results of this train of inquiries.! We 



* The account of this discovery is contained in a memoir which 

 was read at the " Institut." March 24, 1834. 



+ The first of these two laws is termed by Serres, who has zea- 

 lously prosecuted these investigations, " la loi de symmetrie ;" and 



