1896.] OS THE OBLIQTJB septa m TSE *ASSEEiNBS. 225 



with whicli this takes place seems wonderful and to me somewhat 

 analogous to crystallization in inorganic matter. If the elytra are 

 examined from their upper surface, the difference between the 

 larger punctures surrounding the spots and those of the ground- 

 colour is very marked, the latter being irregularly and the others 

 regularly placed ; but if the elytra are removed and examined from 

 the inner side, a thin layer of skin covers the entire surface, but 

 the punctures shine through it and seem of nearly equal size and 

 much more numerous. I may further mention, that all the spots 

 or bands on the upper surface seem slightly convex and show 

 rarely any punctures except round their margins. These are all 

 the observations I am able to record ; and I must leave to anatomists 

 to form any conclusions, if such are possible, as to the way in 

 which nature has worked here, and whether we could obtain any 

 clue by examining the insect in its native place, when immature 

 and in process of formation, so as to get some idea how colour, so 

 distinct from punctuation, can influence the latter or the reverse, 

 when this is apparently the case in so exceptional an instance as 

 the present. The subject itself is not new, having been noticed 

 by Chapuis and myself some years ago, but I think it well to draw- 

 attention to it again, so that more observations may be made, if 



4. On the Oblique Septa (" Diaphragm " of Owen) in the 

 Passerines and in some other Birds. By Frank E. 

 Beddard, M.A., F.R.S., Prosector to the Society, 

 Examiner in Zoology and Comparative Anatomy to the 

 University of London. 



[Eeeeived December 16, 1896.] 



The facts which I bring before the Society have been accumu- 

 lating in my notebook for the last few years, and even now there 

 are numbers of types of Passerine birds which I have not had, and 

 may never have, the opportunity of examining. Less emphasis, 

 therefore, must be laid upon such classificatory conclusions as 

 I venture .to bring forward, than upon the actual facts which I 

 record. There are a certain number of desirable Passerine genera 

 represented in the rich spirit stores of the Prosector's department, 

 but not referred to in the present paper ; I have thought it unwise 

 to make any use of them, since fresh material is so essential for the 

 proper study of delicate and transparent membranes. 



The greater part of the present communication deals with the 

 divergent structure of what Prof. Huxley ' has termed the " oblique 

 septum" in Passerine birds. I may therefore conveniently 

 commence with a description of the normal arrangement of 

 this structure, as it is seen for example in the Duck. And I 

 avail myself of Prof. Huxley's own words': — "The second so- 



1 " On the Respiratory Organs of Apteryx" P. Z. S. 1882. 

 ' ioc. cit. p. 561. 



Paoo. Zooi. Soo.— 1896, No.XV. 15 



