351 MR. R. S. WRAY ON THE MORPHOLOGY [Apr. 5, 



larger proportions, and at the very earliest stages the remiges are dis- 

 tinguishable. At this stage the wing is quite rounded in section, there 

 being no trace of the " ala membrana ;" the next feathers to appear 

 are the t. majores (inferior), closely followed by the other ventral 

 coverts, the other dorsal coverts meanwhile having appeared. At 

 this stage {cf. Plate XXXII. fig. 1) the inferior major and median 

 coverts are distinctly more on the dorsal half of the rounded edge 

 of the wing than its ventral, but very quickly they become quite 

 ventral, owing to the rapid growth of the remiges. This stage 

 is quickly passed over, but sufficient is visible to sliow that these 

 feathers are carried distinctly to the lower surface by inequality 

 of growth {cf. Plate XXXtt. figs. 2-4). The feathers resulting 

 from these are the plumules seen in the wing of the DiickHng, and of 

 no use for flight. The wing of a Duckling reproduces in a great 

 measure, allowing for specialized differences, the adult Ostrich's 

 wing or the Rhea's ; and these wings are survivals of the transition 

 state of the wing, probably never having been used for flight, but 

 having undergone special modifications of their own from that point. 

 It is pretty clear the remiges of the Ostrich and Duck's wing corre- 

 spond, more so the Ostrich and Duckling's ; in the Ostrich we have 

 but one row of ventral coverts, and in the embryo we get them most 

 distinctly on the dorsal side. The Ostrich embryo figured (fig. 2 c, 

 p. 3.51) shows the manus from the ventral surface ; digits i., ir., and 

 III. being well developed ; digit iii. at its tip projecting beyond the 

 general fold of the wing ; in fact there is a very complete webbed 

 manus. The feathers seen (a', fig. 2 c, p. 35 1) are the row of ventral 

 coverts, and lying over digit in. on its dorsal surface are two of this 

 row hidden from sight by it. In the adult, one of these feathers grows 

 over the distal part of phalanx 1 of digit in., owing to elongation of 

 its quills ; here we have the dorsal position actually preserved in the 

 adult. The wing of the Ostrich presents also a primitive condition 

 especially in the cubital region, in that the " ala membrana" is not 

 specialized as in the Carinatae, being in the intermediate condition of 

 the Carinate embryo. Probably the feathers now representing the 

 remiges and the principal coverts were more numerous in the primi- 

 tive wing type, and iiave become restricted in number on the manus ; 

 thus the Ostrich has 16, the Grebes 12, while most birds have only 

 1 1 primaries. 



Wing-Formula. 



The main facts with regard to the feathers of a bird's wing may 

 be expressed as a formula. Denoting the metacarpo-digitals by 

 Md, the metacarpals by m, the digitals by d, and expressing the 

 number of feathers in each group by a number placed after (thus, 

 six metacarpals, m 6), the cubitals by C, " quincubital," "aquin- 

 cubital " by C% we formulate the remiges 



MdU m6 db C'x*. 



The coverts are indicated by o, /3, y, for the t. majores, mediae, 

 and minores respectively ; by placing a figure below the line, thus n^, 



* 0' = number of cubitals, wbicb varies considerably in different groups. 



