200 Mr. H. Seebolim on the 



It follows from this table that in an 8 clays' chick, contrary 

 to what we find in the adult, first the humerus is longer than 

 the radius, and secondly the arm is longer than the hand. The 

 contrast would be greater in this stage if the length of its 

 skeleton could be taken as representing the length of the 

 hand. But this is impossible owing to the absence of a 

 definite boundary to the skeletal parts distally, and there- 

 fore the length of the wing from the radial carpal is taken 

 to represent that of the hand. This stage (that of the 

 8 days' embryo) lasts but a short time. As the above table 

 shows further on, the proportions alter in an embryo of 

 10 days ; the radius is longer than the humerus and the 

 hand longer than the arm — not strikingly so, but still dis- 

 tinctly. From the 10th day onward to hatching there is 

 no further change in the proportions. All three regions of 

 the wing grow at a nearly equal pace. Afterwards, during the 

 nesting-stage, the forearm and, to a much greater degree, 

 the hand grow out of these proportions. It appears that 

 the nestling, as far as its anterior extremity is concerned, 

 becomes a Cijpselus after the time of hatching. The humerus, 

 even on the 16th day, has much resemblance to the definite 

 form, while the hand has to grow considerably. 



As Jeffries (" On the Claws and Spurs of Birds' Wings," 

 Proc. Bost. Soc. Nat. Hist. vol. xxi. p. 301) has already 

 pointed out, the thumb of Cijpselus has a claw. This is first 

 formed on the 10th day. In this stage the second finger 

 also has a slender claw, as I have discovered by a suitable 

 preparation. The claw of the pollex remains for some weeks 

 after hatching ; the claw of the index finger very rapidly 

 disappears. As regards the carpus and tarsus, I shall treat 

 of this subject in my complete memoir. 



XVIII. — An Attempt to Diagnose the Subclass Coraciiformes 

 and the Orders, Suborders, and Families comprised therein. 

 By Henry Seebohm. 

 The Coraciiformes differ from all other birds in the arrange- 

 ment of their deep plantar tendons. There is amongst birds, 



