2 W. P. PYCRAFT. 



and this is especially the case with Prof. Meiizbicr's paper. So much having been done 

 then, it has been my aim rather to extend our survey than to revise the work already 

 mapped out. 



II. — Pterylosis of the Adult. 



In their pterylosis the penguins ditl'er from all other Ijirds, even including the 

 Struthious types ; and this because of the uniformly even distribution of the feathers 

 over the body. The only apterium is found extending in the form of a narrow space 

 from the cloaca upwards to the middle of the abdomen. Even in the Struthious types, 

 which approach nearest to this condition, e.g., Casuarius and Aptery.v, an apterion 

 trunci laterale as well as an apt. mesogastrsei is represented. It is impossible to 

 distinguish remiges or coverts in the wing of the penguins, and the parapteron and 

 hypopteron, as well as the ala-spuria, are all wanting also. 



The rhamphotheca of the penguins is almost universally described as compound. 

 Certainly it appears to be so in genera such as Catarrhactes and Megadyptes, inasmuch 

 as a deep groove extends throughout nearly the whole length of the sheath upper jaw, 

 dividing it into an appaient " rhinotheca " and " gnathotheca," recalling that of the 

 Tubinares. In the remaining genera this groove is much less developed, while in the 

 embryos of all the genera which I have had an opportunity of examining, this groove is 

 either very feebly developed or altogether wanting. On examination of the beak 

 sheath of any of these birds the groove in question will be found to terminate Ijefore 

 reaching the tomium. Thus it would seem that the penguins are in this respect less 

 primitive than has been supposed. From the slight indication of this groove in the 

 embryo we must assume that the simulation of complexity in the beak-sheath of the 

 adult is a secondarily acquired character. In the Emperor and Adelie Penguins this 

 groove is not more marked than in, say, the curlew for example. The anterior nares 

 in the penguins, except in the genus Spheniscus, close up soon after hatching ; they 

 would appear, however, to be functional for a short time, inasmuch as a bristle can be 

 passed through to the posterior choante in very young nestlings. This pecidiarity the 

 penguins share in common with the Steganopodes, the Phsethontidas and Fregatidse 

 only still maintaining functional nares, though extremely reduced. 



It is a point of no little interest to remark that, while in the cormorants and 

 gannets the osseous uarial aperture has become entirely closed, and nearly so in 

 Phsethon and Pelecanus, in the Sphenisei this aperture, in the dried skull, is of 

 considerable size, extending, in fact, nearly the whole length of the beak. This, of 

 course, refers to the adult skull. But in the nestling Sula, and in Phsethon, the narial 

 aperture of the skull is as large as in the Sphenisei. It would thus seem that the 

 closing of the osseous nares follows that of the external sheath only by slow degrees, 

 and may not take place at all. Are we to regard the occlusion of the horny sheath of 

 the external nares as due to adaptation to diving hal)its brought about by selection, 

 and the later closing of the underlying osseous aperture — as in Sida — to the efiects of 



