696 MB. 6EB.ABD W. BTJTLBB OK THE [NoV. 19, 



information of still more recent date, so far as I have seen, either 

 hardly touch upon the subject, or else do not convey a definite 

 and correct impression of the whole matter \ 



(viii.) Lastly Cope [1894 (7) & (8)] has recently published two 

 papers which touch on this subject. These are storehouses of 

 facts, and except with reference to his treatment of this one point, 

 so far as I have been over the same ground, I have very little to 

 do beyond endorsing his statements. But just because his name 

 carries such weight, his treatment of this point is one of the 

 strongest justifications of the publication of this paper. It will, 

 however, be best to defer further reference to these papers, and 

 especially the accompanying figures, to the next section, where I 

 justify the contrary view of the matter. 



III. On the Complete oe Partial Suppression of the 

 Left Lung in Snakes. 



(a) On a means of distinguishim/ the Right Lung from the 

 Left in SnaTces. 



In deciding as to the homology of the lungs of Snakes, in which 

 animals in most cases one is quite rudimentary if not absent 

 altogether, Embryology is of course our surest and best guide 

 when we are able to resort to it. Thus I have serial sections of 

 a number of stages of Tripodonotus natrix which show the early 

 development of the lungs from the first commencement of the 

 shutting off (Lamprey fashion) from behind forwards of the 

 oesophagus from the anlage of the lungs and from the trachea to 

 a time when the lungs have attained a fair size. These show us 

 that it is the left lung, and not the right, which is from the first 

 smaller than the other, and which as the snake grows remains 

 quite rudimentary. T have also early stages of Zamenis gemo- 

 nensis which show in like manner that the functional lung of this 

 second Colubrine also is the right lung. 



As to those Snakes which in the adult show no trace of a second 



* As examples of this later class, and in further justification of this paper, 

 not in any spirit of ungrateful criticism, I may refer to the fullest accounts 

 of the subject that I have come across in the ■works of this type most familiar 

 to English students. 



a. Wiedersheim ['Lehrbuch der vergleichenden Anatomie der Wirbelthiere,' 

 2nd ed. p. 650, Jena, 188fi] speaks of " die Luiigen der Ophidier, wovon sich 

 haiifig, ganz wie bei Gymnopbionen und Amphisbrenen, nur die eine, und 

 zwar die rechte entwiokelt, wahrend die linke entweder gauz schwindet, oder 

 doch meist nur sehr rudimentar erscheint." 



The words, taken by themselves, do not necessarily mean that in the 

 Aniphisbanians it is the right lung that is well developed, but 1 think they 

 naturally tend to produce that impression, especially in the mind of the reader 

 who is sufiiciently interested in the matter to look up the figures of Siphonops 

 (J. c. fig. 454, p. 585) and Amphishtena {I. c. fig. 459, p. 589), for the lung of 

 the latter is there drawn to the right of the trachea and otherwise in the 

 position of a right lung. 



b. Hoffmann, in Bronn's ' Klassen und Ordnungen des Thierreichs,' Bd. vi. 

 Abth. iii. p. 1594 [in a part dated 1886], is responsible for almost precisely the 

 same words as those used by Wiedersheim. 



