MUSCLES OF THE HIND LIMB 97 



In Nycticorax Gardeni, which has no ambiens, there is a 

 difference in the origin of the flexors in question which is of 

 great interest. The two origins from the femur are as in the 

 crane. But there being no ambiens there can be no origin 

 from that muscle. Nevertheless the third head of the 

 flexors is present in the shape (see fig. 53) of a broad ten- 

 dinous band arising from the fibula, which soon divides into 

 the three tendons to the three muscles, precisely as does the 

 tendon of the ambiens. This is highly suggestive of the 

 rudiment of an ambiens, a suggestion which is confirmed on 

 referring to a specimen of Opisthocomus without a fully de- 

 veloped ambiens (fig. 53). And as the herons are birds which 

 are presumed to be really homalogonatous birds, though 

 they have lost the ambiens, the fact is of additional interest ; 

 particularly is this so when we compare the conditions 

 obtaining in Nycticorax with those which characterise 

 Corvus, a clearly anomalogonatous bird, none of whose near 

 relatives possess an ambiens. In Corvus capellanus it was 

 discovered that the flexors usually connected with the am- 

 biens, or with its rudiment, had no origin from the fibula 

 at all, and arose by only a single head from the femur. The 

 same was practically the case with Bubo maximus, only 

 that both femoral heads were present. Now the owls, 

 formerly relegated to the Aocipitres, are more generally 

 looked upon as related to the picarian birds, forming, in 

 fact, a section of the anomalogonatse of Gaerod. The state 

 of their ambiens is entirely confirmatory of this placing. 

 We have some evidence, therefore, that there are degrees in 

 the disappearance of the ambiens, which, so far as the few 

 types that have been examined enable us to say, distinctly 

 support the division of birds into the two great divisions of 

 Gareod. 



Peroneus Superficialis. — Confined as a rule to the tibia 

 in its origin, this muscle sometimes springs also from the 

 fibula. The tendon of insertion, after giving off a branch 

 to the tarsus, becomes attached to the tendon of the flexor 

 perforatus digiti III. This muscle is occasionally completely 

 absent ; this is the case with various Picopasseres, owls, &c. 



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