LECTURE VII. 317 



historian. The department of the anato- 

 mist ends, after having recounted those 

 circumstances which relate to the structure 

 and animal economy of living beings, that 

 are calculated for the purposes just recited. 

 According to this division of the subject, I 

 may mention, that whilst some animals 

 build nests or habitations to cherish their 

 young, others have them formed in their 

 own bodies. Of this I have already men- 

 tioned one instance, when speaking of the 

 marsupial quadrupeds which are ovovivipa- 

 rous. The Pipa or Surinam toad excludes 

 its eggs like other animals of the same kind, 

 yet the young toads become afterwards 

 lodged in separate cells on its back. The 

 pouches of marsupial animals are perma- 

 nent, and they suckle their young, but there 

 are no cells in the back of the Pipa during 

 its unimpregnated state, nor do these cells 

 appear to secrete any thing ; neither have 

 they any communication with the interior 

 of the animal ; all which circumstances 

 Mr. Hunter took much pains to examine 

 and display. Why this great toad should 

 differ in this manner from others of the 



