FAuk 



524 SwAKTH, California Forms of Psaltriparus. [q^j 



in the chain, the young sometimes develop a starthng similarity to 

 the adult female, occasionally even to the adult male, of mclanotis. 

 From the present stud}' it is evident that adults of idumbeus at a 

 point of meeting with minimus are sometimes of the nature of inter- 

 grades towards this western form. 



Ridgway (1904, p. 430) evidently strongly inclined toward a 

 belief in the existence of intergradation between melanotis and 

 plmnbeus, and in the specimens discussed in the present paper there 

 is shown apparent blending between pluinheus and minimus. This 

 somewhat alters our conception of the relationships of the various 

 forms of PsaUriparus, and results in a much closer linking together 

 of the three generally recognized species. I have no intention here, 

 however, of formally proposing the reduction of the known forms of 

 Psaltriparus to subspecies under one species. We obviously can- 

 not express all the inter-relationships of different forms in our no- 

 menclature, and the generally accepted present treatment of the 

 species and subspecies of the genus Psaltriparu.s seems more satis- 

 factory than any such change would be. It seems evident though, 

 that in the three forms, mclanotis, pluviheus, and vnnimus, there are 

 to be distinguished three branches of a parent stem which have 

 diverged to a point where we are just able to detect traces of their 

 former union. 



Through some females and young of mclanotis and young of 

 plumhcus, we can observe apparent blending between these two, 

 for the assumption of features of mclanotis by the young of plum- 

 hcus would appear to be either a reversion to common ancestral 

 characters on the part of the latter, or else it is a rather remarkable 

 case of parallel development, with, in one species, greater specializa- 

 tion in the young than in the old, and specialization exactly such 

 as is shown in a neighboring race. The former belief seems the 

 more reasonable. The mergence of pilumhcus and minimus is of an 

 abrupt and broken nature. From these facts it seems as though the 

 three 'species,' mclanotis, plumhcus, and minimus, had advanced 

 in their evolution to a point where the connecting links were almost 

 eliminated, only faint traces of their former close union still being 

 visible. The intermittent appearance of peculiar characters in the 

 Juvenal plumage of one of the species, and the occasional produc- 

 tion of what appear to be hybrids, may be taken as evidence of this 

 nature. 



