1895.] LXTlfGS OF S]S^AKES, AMPHISBJE>'LDjE, ETC. '707 



VII. On the Eatiokaxe of the Facts eecoeded iif this Paper. 



Taking these Suakes and Snake-like forms together, the facts 

 noted in this paper are that while some agree with other air- 

 breathing vertebrates in having two lungs well developed, some 

 have one lung quite rudimentary or absent altogether, and that of 

 these latter some have the right lung rudimentary or absent and 

 some the left. 



These facts suggest the questions — May we reasonably conclude 

 that in the ancestors of all the different groups of pulmonate 

 vertebrates the lungs were essentially similar in their first origin ? 

 If so, what was probably the most primitive condition ? What 

 significance may we attach to a divergence from such common 

 condition of the kind above described ? 



' I bave also examiued two specimena of Lygosoma verreauxii. In the 

 first I was at first surprised to find the right lung apparently shorter than the left 

 (contrary to the rule), but on further inspection I found that this condition 

 was purely pathological, being due to tlie presence of a small tumour on the 

 anterior border of the right lobe of the liver which interfered with the expansion 

 of the lung. In a second specimen the lungs were of precisely equal length. 

 This equality of the lungs in L. verreavxii and occasionally in Anguis fragUis 

 (see list) makes me expect that (while the elongated snake-like form and the 

 reduction or suppression of the limbs are commonly associated with the reduc- 

 tion of one lung) llie lungs may be found equal in a number of the other 

 elongated small-limbed lizards of which there are so many, especially in the 

 family Scincid<e. 



^ 3. von Bedriaga (Archiv fiir Naturgesehichte, 1884, Bd. i. p. 63) finds no 

 trace of a second lung in Blanus {Amph.) cinereits and B. strauchii and Trogo- 

 nophis wiegnianni ; and C. Smalian (Zeitschrift fiir wissensch. ZooL, Bd. xlii. 

 pp. 188 & 189, 1885) finds no trace of a second in A.fuliginosa, B. cinereus, and 

 Anops Jcingii, while as to Trogonophis wiegmanni he curiously prefers to regard 

 it as having a bilobed single lung instead of a pair of lungs. Neither Bedriaga 

 nor Smalian, so far as I have discovered, say which luug is well developed, but 

 Bedriaga's figures of .B. cinerea (l. c. pi. iv. figs. 2, 3) rightly represent it as the 

 left. 



^ I have examined other Amphibia, especially the elongated forms with weak 

 limbs and reduction of digits or absence of one pair of limbs (Siren); but in 

 none of them can one lung be said to be atrophied as compared with the other. 

 In most of them the two lungs are of equal length [Siren lacertina, Menohran- 

 ckiis lateralis, Menopoma alkghanense, Salamcmdra maculosa, Triton cristatus, 

 Amblystoma tigriniiiH {faiv-BxzzAs'peciTa&'as o? A-xolotY)]. In a few cases there 

 is a difference in the length. Thus in ^m^/»W/Ma the right lung is the longer, 

 while in Proteus anguinus, as is known from the pubhslied figures, the left is 

 somewhat the longer, and the same appeared to be the case in some small 

 specimens of Axolotl. These last two can hardly, however, be regarded as 

 exceptions to the general rule, for we cannot say that the right lung is atrophied 

 as compared with the left. Thus each lung of Proteus extends back to the 

 ovarj' or testis, and the fact that the right lung is the shorter depends on the 

 fact tliat in accordance with a common habit the right reproductive gland is 

 situated further forward than the left. Again, though recording it for form's 

 sake, I hardly think any stress should be laid on the right lung appearing 

 shorter than the left in small (3 inches long) specimens of Axolotl. The lungs 

 are equal in later stages, and the apparent difference in the younger specimens 

 is probably due to the small intestine, which inclines to the right side, presenting 

 the complete expansion of the terminal portion of the right lung, which projects 

 backwards freely beyond the termination of the lung ligament. 



