215 
Birds of New Zealand. 
so many intermediate forms, that even the supposed line of 
division between both sexes is exceedingly difficult to draw. 
Moreover (and this is peculiar to Dinornis maximus) there are 
scarcely two skeletons entirely alike; there are some which 
have a remarkably long metatarsus, whilst the other leg-bones 
do not (at least at the same rate) increase in size; others are 
much stouter for their height. Altogether we might trace 
the same peculiarity in size and form as in a series of human 
skeletons selected at random. 
The same is the case with the skeletons of the immature 
birds of this species, of which we possess portions from the 
chick to the full-grown giant bird, where the tarsal epiphysis 
is not yet so closely united with the metatarsus, that the line 
of junction is still visible, where also a similar variety of form 
can be traced. 
The difference in size between Dinornis maximus and Di¬ 
nornis rohustus , the next in size, is very marked and constant. 
Of the latter we obtained a series of two sizes, of which the 
largest might be assigned to the female. 
Between Dinornis rohustus, ingens, gracilis , and struthioides, 
besides their well-defined specific characters, there are also 
distinct breaks, each species possessing at the same time two 
constant sizes. 
Of Meionornis casuarinus a series of four clearly defined 
sizes are in our possession; so that we might conclude that 
we have two closely allied species before us, of which the two 
largest sizes represent male and female of the one, and the 
two smaller male and female of the other. 
A considerable difference in size occurs between the smallest 
species of Meionornis casuarinus and the largest species of 
Meionornis didiformis. In the latter we can distinguish also 
four sizes, with a gradation similar to that observed in the 
former; so that I am led to believe that this species, like Mei¬ 
onornis casuarinus, consists of two subspecies. 
If we compare two skeletons of Apteryx australis, male and 
female, and two of Apteryx owenii, male and female, with 
each other, a similar distinct gradation is observable. 
Palapteryx elephantopus has also four well distinguishable 
