396 Darwin, and after Darwin. 
so exclusively related to the sexual relationship on the 
other. 
Finally, we must take notice of the fact that where 
peculiar s¢rwctures are concerned for purposes of dis- 
play in courtship, the elaboration of these structures is 
often no less remarkable than that of patterns where 
SSeS ADULT MALE 
Fic. t24—The Bell-bird (Chasmorhynchus niveus, } natural size). 
Drawn from nature (2. Coll, Surg. Alus.\. In the drawing of the 
adult male the ornamental appendage is represented in its inflated 
condition, during courtship; in the drawing of the young male 11 is 
shown in its flaccid condition. 
colours are thus concerned. Take. for example, the case 
of the Bell-bird, which I select from an innumerable 
number of instances that might be mentioned because, 
while giving a verbal description of this animal, 
Darwin does not supply a pictorial representation 
