4 Jones — Nestling Feathers. 



Sumner, Director of the U. S. Fish Commission. To Capt. Vinal N. Ed- 

 wards, of the Fish Commission, I am indebted for many valuable hints and 

 advice relating to the habits of these birds; and to Dr. R. M. Strong, for 

 valuable suggestions and advice. 



II. MATERIAL. 



Material for histological and cytological study was obtained from the 

 following birds: Sterna hirundo, S. dougalli, Larus atricilla, and Merula 

 migratoria. Developing feathers were also secured from the chick and do- 

 mestic duck, incubated both artificially and naturally. Dry feathers with 

 downs attached for grosser study came from the following sources: Mr. H. 

 C. Oberholser, under the direction of Dr. T. S. Palmer, from the U. S. 

 National Museum collections; Mr. Frank M. Chapman, from the Ameri- 

 can Museum of Natural History; Messrs. C. C. Adams and N. A. Wood, 

 from the collections of the University of Michigan; Prof. E. L. Moseley, 

 from his private collection of American and Philippine birds; Dr. N. Dear- 

 born contributed both alcoholic and dry material from the Field Colum- 

 bian Museum; and Dr. C. O. Whitman, fresh material from his pigeons. 

 To all of these gentlemen I wish to express my thanks. The collections of 

 Oberlin College furnished some material not obtainable elsewhere. 



III. METHODS. 



The following fixing fluids were used for chicks from five to twenty 

 days' incubation: (i) Kleinenberg's picro-sulphuric mixture, (2) saturated 

 aqueous solution of corrosive sublimate, (3) Hermann's fluid, (4) alcohol- 

 formaldehyde mixture (70% alcohol 98 parts, 40% formaldehyde 2 parts). 

 After proper fixation, pieces of skin containing the desired structures were 

 cut away and later treated as ordinary histological tissues. 



For the latest stages, Hermann's fluid was found somewhat superior, 

 but for the earlier stages the alcohol-formalin mixture gave the most satis- 

 factory results. Since most of the material must be put into the killing and 

 fixing fluids on the collecting grounds to insure a normal condition of the 

 cellular structure, the latter reagent was the only one found practicable, be- 

 cause the tissues could remain in it indefinitely without material injury, 

 while more than five hours in the others proved fatal to good results. It 

 was usually necessarj^ to remain in the field for an entire day, because the 

 nearest collecting ground was five miles away by water. Furthermore, after 

 the alcohol-formalin fixation the tissues stain equally well in any of the 

 stains used, even the iron haematoxylin. For the earlier stages, the Her- 

 mann's fluid did not give good fixation, and it was always likely to blacken 

 the tissues unequally and unduly. The picrosulphuric was very diflScult to 

 handle because it required a great length of time for washing out before 

 stains could act; even after two weeks of careful washing, staining was usu- 



