102 Transactions. — Zoology. 



species in the two Islands which are nearly of the same size 

 are truly representatives of each other, or whether they form 

 two parallel lines of development, one in each Island, both of 

 which are descended fi-om D. struthioides. To join the species 

 together would delay the settlement of this question. 



Sexual Differences. 



In his second paper on Dinornis, Professor Owen discussed 

 the question whether some of his species might not be the oppo- 

 site sex of others, and came to the conclusion that the}' were 

 not so/'' "With this conclusion I quite agree. A. didiformis 

 has no near ally, and must therefore contain individuals of 

 both sexes. It is the same with Palapteryx, of which there is 

 onl}; one species in each Island. S. casuarinus and M. didinus 

 are not likely to be male and female, because their heads differ 

 so much; and, if they are not a pair, each of these species 

 must contain individuals of both sexes in the North Island, 

 and, consequently, in the South Island also. If D. struthioides 

 is only one sex, then the opposite sex must have had different 

 forms in the two Islands — D. torosus in the South, and D. 

 gracilis in the North. But D. torosus and D. struthioides can- 

 not be the two sexes of one species, because they have 

 different geographical distributions, D. torosus being almost 

 entirely confined to the north part of the South Island, while 

 D. struthioides was more abundant in the south than in the 

 north. It is the same with G. geranoides and C. curtus, the 

 former being more abundant in the south-eastern, the latter in 

 the north-western, part of the North Island. And if this is 

 true for six of the genera we may be sure that it is true for 

 Euryapteryx also. 



Sir Julius von Haast has on several occasions stated his 

 opinion that several species of moa consist of individuals of 

 two distinct sizes, with no intermediate forms, which he took 

 to be male and female, and he refers to specimens in the 

 Canterbury Museum as confirmatory of this opinion.! Un- 

 fortunately, he never published any measurements showing 

 these supposed sexual differences, and the collection he refers 

 to in the Canterbury Museum by no means bears out his state- 

 ment. Dr. Haast had specially named S. casuarinus as one 

 that showed these sizes, and I therefore published, in 1874, 

 measurements of all the bones of this species found in the 

 swamp at Hamilton ;:[ and these show a gradual passage from 

 the smallest to the largest. In the following year Mr. Thorne 



* Ext. Birds of N.Z., p. 90. 



t Trans. N.Z. Inst., vol. i., p. 81, and vol. vi.,p. 425; Geol. Cant, and 

 West., 1879, p. 433. 



X Trans. N.Z. Inst., vol. vii,, p. 278. 



