640 SUMMAKY OF CURRENT RESEARCHES RELATING TO 



ureteral dilatations and constrictions, and these he interprets as heri- 

 tages from the Wolffian body enhanced by environmental factors. 



Hares and their Allies.* — M. W. Lyon, jun., has made a mono- 

 graphic study of the hares and their allies, discussing the genera and 

 sub-genera of the existing Leporidas and Ochotonidas, their dental, 

 cranial, and other skeletal characters, their geographical distribution, 

 and their probable relationships. 



Influence of Unilateral Horn-Growth on Cranial Characters.! — ■ 

 J. Ulrich Duerst has made a careful study of the numerous changes 

 which are seen in the sheep's skull when the horn is removed from 

 one side. 



Compound Rhamphotheca of Birds.} — Einar Lonnberg seeks to 

 show that the bill of birds is only a modification of certain common 

 reptilian characters. It is well known that the horny sheath of the bill 

 of some birds consists of several pieces, which are more or less distinct 

 in different genera and species. Lonnberg believes that there are pieces 

 of the compound or " simple " bill of birds which are homologous 

 with the reptilian rostrale, labialia, nasalia, and internasalia of the upper 

 jaw, and with the mentale (or symphysiale), infralabialia, and subman- 

 dibular ia of the lower jaw. 



As long as the ancestral birds were provided with teeth, the horny 

 covering was of less importance, but with the loss of teeth the condition 

 was changed. The premaxillas increased, the rnaxillae decreased, and an 

 enlarged rostrale developed. The mentale was developed in a corre- 

 sponding manner. With the increased development of the premaxillary 

 and reduction of the maxillary tract, it is probable that the anterior 

 labialia were enlarged and the posterior more or less reduced. The 

 author works this view through the chief types of birds in an interesting 

 and suggestive paper. 



Middle Ear and Columella of Birds. § — G. Smith gives an account 

 of the disposition of the chorda tympani in Gallus and Columba, and 

 embryological data concerning the derivation and homology of the 

 stapes. Positively, it may be stated that in the chick the contribution 

 of the auditory capsule to the columella is exceedingly small, probably 

 confined to the foot plug of the stapes ; at any rate, the main part of 

 the stapes, and the whole of the columella, are formed from the hyoid 

 arch. Negatively, the author shows the futility of basing arguments 

 upon this question on isolated stages or on cartilaginous stages which have 

 not been traced back to their earliest procartilaginous forerunners. The 

 conclusion to be drawn is that the stapes of Sauropsida corresponds to 

 that of Mammalia and to the hyomandibular of fishes. Mammalia and 

 Sauropsida have this much in common, that they have both converted 

 the hyomandibular or dorsal portion of the hyoid arch into the stapes, 

 but subsequently they have gone on different lines in evolution, the 



* Smithsonian Misc. Collections, xlv. (1904) pp. 321-47 (27 pis.). 

 t Vierteljahrschr. Nat. Ges. Zurich, xlviii. (1903) pp. 360-75 (2 pis.). 

 t Arkiv f. Zool., i. (1904) pp. 473-512 (13 figs.). 

 § Quart. Journ. Micr. Sci., xlviii. (1904) pp. 11-22. 



