No. 573] 



PATTERN DEVELOPMEN T 



555 



further shown by the fact that one half only may be pres- 

 ent as in the gulden winded warbler recorded by Dr. C. 

 W. Townsend (1908). 



The first category, in which the neck is uniformly pig- 

 mented is illustrated by many of the duck tribe, and 

 probably involves the normal primary patches only. 

 The primary patches are usually restricted first antero- 

 ventrally producing a white throat. Often this is carried 

 dorsally so as to form a white ring around the upper 

 part of the neck by the separation of the neck patch from 

 the crown and the ear patches. Again, if the neck patches 

 are restricted posteriorly a white ring is formed at the 

 base of the neck, a common permanent character in many 

 species. The peculiar little goose-like bird— Nettapn*. of 

 India— has developed this type of marking so that its 

 white neck is encircled by a narrow black ring, and the 

 Labrador duck (Camptorhi/Hclui.s) lias a nearly similar 

 mark (Fig. 57). Other ducks, e. g., the mallard, have the 

 white ring at the base of the neck, only. 



In an interesting paper on the geese occurring in Cali- 

 fornia, Swarth (1913) has pointed out that in the cack- 

 ling goose {Brant a c. minhta) there is much variation in 

 the amount of white on the head and neck. Figs. 58 to 

 62 are traced from a series of photographs illustrating 

 this paper and show the throats of five specimens. The 

 wide range of variation in these specimens indicates to 

 my mind that this goose is in process of reducing the 

 neck patches, and thereby developing a white collar, such 

 as is present in the mallard, and perhaps also a white 

 throat. The usual condition seen in Br ant a canadensis 

 and in so-called normal specimens of />. c. minina is seen 

 in Fig. 58. The white cheeks have been developed long 

 ago in the history of the species, in part perhaps by the 

 depigmentation of the ear patches. Xow a second change 

 is taking place in one of its subspecies. Thus in Figs. 59, 



61 and 62, the neck patches have been reduced poste- 



62 these patches have been restricted anteriorly pro- 



