460 Wetmore, Development of the Stomach in Euphonias. [oct. 



The outcome is readily seen. Through a long period of subsis- 

 tence on a peculiarly specialized food the ordinary form and muscu- 

 larity of the stomach has been lost through disuse and specializa- 

 tion until it has been changed to the simple membranous sac con- 

 necting the oesophagus and duodenum, now characteristic of the 

 Euphonias, a digestive tract which is so arranged as to permit the 

 rapid and unobstructed passage of food through the entire length 

 of the canal. 



The Euphonia, furthermore is enabled to increase its own food 

 supply as the seeds unharmed by digestion are excreted and cling 

 by their adhesive coating to the limbs of the trees, starting new 

 plants which, when mature, produce a new crop of berries. Though 

 in some parts of the United States, notably Louisiana and Texas, 

 mistletoe plants increase until the tree host is killed, in Porto Rico 

 they cause little apparent damage and no effort is made to keep 

 them down. They were noticeably more abundant on the dry 

 south coast, where the air soon hardened the gum surrounding the 

 seeds, than they were on the rain swept north slopes of the moun- 

 tains, where seeds dropped by the birds are liable to be washed off 

 before germination and attachment. 



Some forms of the family Dicfeidae notably DiccEum hirundina- 

 ccum of Australia are called mistletoe birds, and are said to feed 

 extensively on the berries, but I can find no satisfactory description 

 of their stomach. The Robin, Bluebird, Cedar Waxwing and others 

 which occasionally feed on mistletoe berries in the United States 

 do so locally or rarely and use this food merely to supplement their 

 ordinary diet. In my studies I have been restricted to* the investi- 

 gation of the Porto Rican Euphonia, through lack of other material 

 but as parasitic plants of the family Loranthacea^, belonging to 

 either the genus Phoradendron or to others more or less closely 

 allied, are found all through tropical America in the range of the 

 Euphonias we may suppose that they are utilized as food by these 

 species as by the bird which I have studied. This habit sufficiently 

 accounts for the peculiar stomach found in the group as a whole. 



To recapitulate, the Euphonias have long been noteworthy for the 

 aberrant form of the stomach. In studying the species found on 

 Porto Rico it has been found that it feeds entirely on the berries of 

 mistletoe {Phoradendron spp.) a food readily assimilated and one 



