692 MB. GBKAKD W. BTJTLEE ON THE [N^OV. 19, 



describes Snakes (as known to him) as having but one lung ^. 

 We find this view repeated without qualification so late as 1805 

 in a work for which Cuvier is responsible ". 



It would seem that Nitzsch [1808] was the first to describe the 

 rudiment of the second lung (which, be it noted, he rightly speaks 

 of as the left lung) in the Common Snake {Tropic! onoUis natncc), 

 and to suggest that this rudiment would probably be found in 

 many otber Snakes (l)^ 



Since 1808, thanks to such workers as Meckel, Cuvier, Du- 

 vernoy, Stannius, and Cope, our information on the subject has 

 been largely augmented. 



In a sense it may be said that, excluding details, there is little 

 in this paper which has not been stated or hinted by some one 

 previously. But it is equally true that there is httle here which 

 has not been as categorically denied by some one else of equal 

 authority. 



It has thus happened that an interesting generalization has so 

 far been missed. 



This is doubtless in part due to the fact that no one person has 

 given special attention to the matter in all the groups of animals 

 concerned, but in part also to error of interpretation, or error or 

 looseness of description on the part of observers, and in part 

 perhaps to want of caution on the part of compilers when 

 summing up. 



However this be, it seems well to have the facts placed clearly 

 on record now. 



When studying the pleuroperitoueal spaces and membranes of 

 Lizards, Snakes, &c., iu the years 1889-1892^, I of course had to 

 note the relations of the lungs, and I was much struck by the fact 

 that whereas in the AmphisbsBuidse it was always the right lung 

 that was reduced or absent, in Snakes and in other Snake-like 

 Lizards it was the left. 



When I came to enquire what had previously been written on 

 the subject, I found that there was no satisfactory summing up of 

 the whole matter, and that so far as separate animals or groups of 

 animals were concerned, while some previous statements har- 

 monized with my observations, others of equal authority ran 

 counter to them, while, thirdly, many writers did not commit 

 themselves one way or the other. I have accordingly been over 

 my old observations, and supplemented them by others, with the 

 result of only confirming and widening the generalization at first 

 arrived at, which is' — [I of course speak only of the animals 

 examined, see lists, § VI.] — that the Amphisbcenidce stand alone 



^ Aristotle's 'History of Animals ' (R. Creswell's translation in H. G. Bohn's 

 " Classical Library "), Book ii. chap. ii. § 12, p. 44 (London, 1862). 



^ ' Legons d'Anatomie eomparee de Georges Cuvier, reciieillies et publiees 

 sous sesyeux par G. L. Duvernoy,' torn. iv. pp. 323 & 347 (Paris, 1805). 



^ See Bibliography at the end of this paper. Throughout the paper the 

 large numbers in brackets inserted in the text refer to the corresponding work 

 in the list at the end. 



^ Proc. Zool. Soc. 1889, pp. 4.?2-474, and 1892, pp. 477-498. 



