922 ME. F. E, BEDDARD OX TWO SPECIES [DeC. 14, 



significance. If it be achnittecl that the fibrous seam connected 

 with the bronchus is tlie degenevate equivalent of a fiirthei- 

 extension into the lung of the bronchus, it follows that the 

 brandling of this seam is a trace of a former branching within 

 the lung of the bronchus. In fact, that we have in the snake's 

 lung evidence of a reduction to its present simplicity fiom a lung- 

 more like that of a Tortoise or Crocodile, or — and this com- 

 parison may be better — a Taranvs. For in these lattei' types 

 the intra pulmonaiy region of the bronchus is branched or shows 

 traces of branching. In this case the simple character of the 

 lung of the Boidte is not to be strictly compared with the simple 

 sac-like lung of, e. g., Hatteria. For the latter exhibits, as I 

 believe, a primitive state of affairs, and is not much more evolved 

 than the lung of an Amphibian, while the former may have 

 returned to the simple condition through degradation. 



We may now contrast the structure of the lung in Boa occklen- 

 talis with that of B. madagascariensis. In the latter species each 

 bronchus enters its lung, and there is thus, as in B. occidentalism an 

 intrapulmonaiy bronchus. But the intiapulmonaiy bronchus is 

 very short in the case of both lungs, though the larger lung has 

 a rather longer intrapulmouary bronchus. I foiuid that the 

 measurements wei'e seven eighths of an inch in the case of the 

 larger lung and three eighths in the case of the smaller lung ; 

 thus the intrapulmonaiy bronchus was in the larger lung about 

 double the length of that of the smaller lung. It is clear, there- 

 fore, that there is here a very great difference both actually 

 and proportionately (as concerns the two lungs), between the 

 Madagascar species and the Neotropical species which are con- 

 sidered in the present communication. Furthermore, there is 

 not a marked seam continuing down the bronchus in the case of 

 either lung. There appears to be one ; but when the lung tissue 

 is stretched the seam disappears. This is analogous to what 

 I have described in CoraUus. We have therefore a second im- 

 portant difference in the structure of the lungs between Boa 

 occidentalis and its Madagascar ally. 



I have already desciibed or confirmed the description of the 

 intrapulmonary bronchi of the two American species * Boa 

 constrictor and B. diviniloqtta. In both of these the bronchus 

 extends a long way down into the interior of the larger lung 

 exactly as I have just shown to be the case in B. occidentalis. 

 With regard to the extension of the bronchus into the smaller 

 lung, it would appear that Boa occidentalis occupies a position 

 exactly intermediate between the two other species. For in 

 B. diviniloqua the bronchus extends for a goodish way into this 

 lung, while in Boa constrictor there is no intrapulmonaiy 

 bronchus at all within the smaller lung. In any case there is a 

 general agreement between the three Neotropical species of Boa 

 dealt with in the present communication, and a difference 



* P. Z. S. 1906, p. 516. 



