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Show 696 MR. GERARD W. BUTLER ON 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 bis 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 OR PARTIAL SUPPRESSION OP THE LEPT LUNG IN SNAKES. (a) On a means of distinguishing the Right Lung from the Left in Snakes. 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. I 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 1 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, 1886] speaks of " die Lungen der Ophidier, wovon sich haiifig, ganz wie bei Gymnophionen und Ampbisbaenen, nur die eine, und zwar die rechte entwickelt, wahrend die linke entweder ganz schwindet, oder doch meist nur sehr rudimentar erscheint." The words, taken by themselves, do not necessarily mean that in the Amphisbsenians it is the right lung that is well developed, but I think they naturally tend to produce that impression, especially in the mind of the reader who is sufficiently interested in the matter to look up the figures of Siphonops {I. c. fig. 454, p. 585) and Amphisbcena (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. |
