1888.] 



Presents. 



487 



undergone distinct retrogression, being only 0'15 mm. in length, and 

 formed of indifferent tissue instead of hyaline cartilage. From this 

 it would appear that the fifth metatarsal actually disappears in 

 Apteryx instead of fusing with the fourth as in the chick. 



In Stage Gr the proximal tarsals are closely applied to hut have not 

 yet united with the tibia ; the distalia also are still distinct from the 

 metatarsals. The rudiment of the mesotarsal semilunar pad has 

 increased considerably, and in the centre of it a rounded nodule of 

 hyaline cartilage has appeared, which I take to be the representative 

 of the centrale tarsi, an element not hitherto recognised in birds.* In 

 a recently-hatched specimen of Apteryx australis, it is a perfectly 

 distinct cartilage about 2 mm. in diameter, imbedded in the fibrous 

 tissue of the semilunar pad ; in the adult it becomes ossified, attaining 

 a diameter, in A. oiveni, of about 5 mm. 



As the scientific libraries to which .1 have access are small and 

 imperfect, I take this opportunity of saying that I shall be extremely 

 grateful to the authors of papers bearing upon the subjects of the 

 present investigation who will favour me with separate copies. 



[Note. — In no stage is there any trace of the hard knob on the beak » 

 which in birds generally assists the embryo to break the egg-shell. — 

 March 21, 1888.] 



The Society then adjourned over the Easter Recess to Thursday, 

 April 12th. 



Presents, March 22, 1888. 



Transactions. 



Baltimore : — Johns Hopkins University. Circular, No. 63. 4to. 



Baltimore 1888; Studies (Historical and Political Science). 



Ser. 5. No. 12. 8vo. Baltimore 1887; Report, 1887. 8vo. 



Baltimore 1888. The University. 



Birmingham : — Free Libraries. Report, 1887. 8vo. Birmingham 



1888. The Committee. 



Edinburgh : — Royal Scottish Society of Arts. Transactions. Yol. 



XII. Part I. 8vo. Edinburgh 1881. The Society. 



Kew: — Royal Gardens. Bulletin. 1888. No. 15. 8vo. London. 



The Director. 



London : — British Museum (Natural History). Catalogue of the 

 Fossil Mammalia. Part Y. 8vo. London 1887 ; Catalogue of 



* It was figured, but not described, by Morse (" On the Intermedium," ' Anni- 

 versary Mem. Boston Soc. Nat. Hist.,' 1880, Plate I) ; and is figured and described 

 as naviculare vel " centrale" by me in my paper "On the Morphology of Birds." 

 (See Abstract, 1 Boy. Soc. Proc.,' vol. 42, 1887, p. 58.)— W. K. P. 



2 m 2 



