228 NEW MORK ZOOLGCICAL, SOClEIN 
—the flat, keelless sternum—all need of surface for the insertion 
of flight muscles having ceased long ago. 
The increase in size and power of the legs is perhaps the most 
obvious adaptation of all. A two-fold function has resulted from 
this change from the more slender, ancestral hind limbs. The 
struthious birds have acquired the power to flee swiftly from dan- 
ger, and in addition, when at bay, or in defence of their young, 
the massive development of leg and foot provides them with very 
formidable weapons of defence. 
In Apteryx alone, in which the cursorial habit 1s perhaps least 
developed, there are four toes. Emeu, Cassowary and Rhea have 
three, while the Ostrich has but two. This latter bird shows an 
interesting parallelism with the mammalian genus Equus, in the 
development of one toe at the expense of the others. At college 
an athlete is told to run on his toes alone, and, instinctively, 
throughout all time, those creatures, which have had to run for 
their lives in life’s great race, have followed this rule. The horse, 
the kangaroo and the Ostrich have never broken training, and 
all are tending toward the one-toed condition of the first-men- 
tioned animal. In the kangaroo the fourth toe is the dominant 
one; in the other two animals it is the middle, or third toe, upon 
which all the stress comes. 
The voice of the struthious birds is as primitive as many of 
their other characteristics, and, though they have traces of some 
kind of an ancestral syrinx, yet their utterances are in keeping 
with their massive frames—reverberating rumbles, booms and 
roars, which latter vocalization in the Ostrich so much resembles 
the roar of a lion that it may be somewhat of a protection against 
their natural foes. 
Mr. J. G. Millais in his “Breath from the Veldt” says that the 
difference between the utterances of the two creatures is in power 
rather than in quality or sequence of sounds. He illustrates them 
in this way: 
LION 
(crescendo) (diminuendo) 
Moan-ROAR - R-O-A-R-ROAR-Roar-roar-Grunt-grunt-grunt-grunt-grunt-grunt 
(dying away). 
OSTRICH 
(crescendo) 
ROAR-ROAR-ROAR-ROAR-R-R-R-R-R (prolonged). 
