94 H. H. COLLINS 



7. SUMMARY 



1. The process of normal moult has been followed in a large 

 series of living mice representing several species of Peromyscus. 



2. In this study of the living material, the process of moult 

 is found to be, in a measure, comparable in regularity of sequence 

 and directions of growth with the moults of birds. 



3. In the postjuvenal moult, growth occurs more or less in- 

 dependently on certain regions of the body, suggesting the mode 

 of moult in the pterylae of birds. 



4. The moults of adults are generally of a more irregular 

 character. 



5. In 3'oung mice the change of pelage is quite obvious, but 

 in adults it may be quite insidious and evident only upon close 

 examination. 



6. In general, the process of moult is quite similar in different 

 species, but in some instances there appear to be certain minor 

 differences. 



7. By plucking out juvenal hair, the precocious appearance 

 of the postjuvenal pelage may be induced. 



8. Under certain conditions, the appearance of this postjuvenal 

 pelage, after artificial removal of the juvenal, is preceded by the 

 outgrowth of an aberrant type of hair which persists only for a 

 short time. Within these hairs the localization of pigment is 

 abnormal. 



9. The normal sequence of the incoming hair is profoundly 

 modified bj^ artificially induced regeneration. 



10. Restoration of pelage in adults occurs irrespective of sea- 

 son, after the plucking out or clipping of the old hair. 



11. This restoration is accomplished by the outgrowth of new 

 hairs, except in case of the vibrissae, which are replaced by the 

 elongation of the cut hairs. 



12. Restoration is much more rapid when the hairs are plucked 

 out than when merely cut. 



13. The differences in coloration of the old and the new pel- 

 ages as seen on opposite side^ of the body of adult gambeli are 



