SCIENCE AND DANCING 171 



man or animal implies a sense of rhythm. Though not 

 common amongst animals, it is exhibited by many birds, 

 by spiders, and by some crustaceans ! Rhythm is an 

 essential feature of the sequence of sounds which we call 

 " music." The singing of birds is related to their per- 

 ception of and pleasure in rhythm, and it is not, there- 

 fore, surprising that they should also dance. It is, 

 however, curious that the birds which " dance " are not 

 the " singing birds," and that there are many birds which 

 neither sing nor dance. The dancing of birds is usually 

 part of the " display " of the males for the purpose of 

 attracting the females at the breeding season. It is well 

 known in some African cranes, as well as in rails and 

 other similar birds, and may be witnessed at the 

 Zoological 'Gardens in London. Other birds " strut " 

 rather than dance, whilst displaying their plumage, as, 

 for instance, the turkey and pheasant tribe and the 

 bustards. Parrots and cockatoos will often make a 

 rhythmical up-and-down movement of the neck in time 

 to music, but usually the " dance " is the accompaniment 

 of definite emotion. The male spider of some species 

 courts the female by making dancing movements and 

 posing itself in a very curious way, so as to display a 

 spot of bright colour on the head to her observation. 

 The same kind of movement and action has been 

 observed in marine shrimp-like creatures. Some spiders 

 are excited and made to dance by the vibrating note of 

 a tuning-fork set going near them. I once had the 

 chance to observe a male octopus in the aquarium at 

 Naples, who was displaying himself to the female, 

 changing colour rapidly from one shade to another, and 

 rolling his long sucker-bearing arms in the form of 

 spirals. Probably one should not consider this as a 

 " dance," since no rhythmic interruption or succession of 

 movements was observable. 



