502 STUDIES, SCIENTIFIC AND SOCIAL chap. 



In the chapter on " Some Habits and Instincts of the 

 Pairing Season," the songs, dances, and displays of 

 j)lumage by birds are described, and Professor Lloyd 

 Morgan seems inclined to the conclusion that their great 

 development indicates the action of that form of sexual 

 selection termed " preferential mating." Some additional 

 observations are quoted which support this view, but the 

 final conclusion is that — " in all these matters further and 

 fuller evidence from direct observation is to be desired." 



The next chapter is on " Nest-building, Incubation, and 

 Migration," and affords much matter for careful con- 

 sideration. As to nest-building the present writer has 

 always urged that careful experiments are required before 

 we can accept as instinctive the building of a peculiar 

 type of nest by each species of bird ; and we find a few 

 such recent experiments now adduced. But when we 

 remember how such a careful experimenter as Spalding 

 was led to wrong conclusions through not varying his 

 experiments sufficiently, the few experiments yet made 

 on nest-building under conditions by no means rigid and 

 with results not described in sufficient detail, can hardly 

 be accepted as settling the question. This is one of the 

 problems that can only be finally settled by experiments 

 tried on a large scale and with every precaution, and the 

 results preserved for comparison and study ; and if ever 

 an experimental biological farm is established this subject 

 of nidification would form one of its most valuable and 

 comparatively easy inquiries. 



The Migratory Instinct. 



Passing over a very interesting discussion as to the 

 habits of the cuckoo and their probable origin, and one 

 hardly less interesting on the habit of the lapwing and 

 many other birdsof simulating injury to distract attention 

 from nest or young, we pass on to the broader and more 

 important subject of migration, which, however, is rather 

 briefly treated. The evidence now accumulated seems to 

 justify Professor Lloyd Morgan's conclusion, that while the 

 migratory impulse is innate, yet, " the element of tradi- 

 tional guidance may be effectual, in the migration stream 



