Systematic Position of the Sheath-hills. 127 



with this subject seem to call for comment. Prof. Studer 

 (/. c), for instance, has stated that the horny sheath which 

 embraces the base of the upper mandible protects the nasal 

 orifices when the bird is feeding on the e£;gs of Cormorants 

 and Penguins, of which it is very fond. That this is a 

 physical and anatomical impossibility will, I think, be 

 apparent to anyone who has examined the bill of a Sheath- 

 bill. Moreover, this sheath varies in its morphology, not 

 only in different genera, but in different species of the same 

 genus, e. g. Chionarchus. 



The same author also states that the chick on hatching 

 is blind (that is to say that the eyelids are unopened). 

 Prof. Studer, I presume, is simply quoting from informa- 

 tion supplied to him, but unfortunately does not give his 

 authority. The question is a very interesting one, because 

 if the young of tiie Sheath-bills are in truth ''blind'" on 

 hatching, we have a very anomalous condition, since, so far 

 as I am aware, there is no other proved instance of it in the 

 Waders. From an examination of a fine series of embryos 

 of Chionarchus minor collected during the 'Challenger' Expe- 

 dition (1873-6), and which are preserved in spirit in the 

 British Museum collection, I at first came to the conclusion 

 that the condition of the eyelids (which were in all cases 

 open) proved beyond doubt that the chick is not "born" 

 blind. However, since reading a paper by Dr. Casey A. 

 Wood* on "The Eyelids and Lacrymal Apparatus of Birds" 

 (' Oi)hthalmology,' Seattle, U.S.A., July 1915), I have to 

 acknowledge that the open-eyed condition in the embryo- 

 chick appears to prove nothing of the sort. Dr. Wood, for 

 instance, says: "Unlike man and many other mammals, 

 there is no true union of the conjunctivae of the two lids 

 before a bird is born. In the Sparrow {probably in all 

 the Passeriformes) the lids are wide open during embryonic 

 life, but as soon as the bird is hatched the eyes are closed, 

 and remain closed for several days. There is no evidence 

 that any organic union occurs between the lid-margins in 

 these ' born-blind ' birds. In all probability the closed eyes 

 * See also notice on p. 174. 



