" quiktocubitaltsm: " in the wing of birds. 225 



Osteological Characters. 

 I have not yet proceeded so far with the collection and colla- 

 tion of osteological facts in pigeons as I have done in the case 

 of the muscular anatomy, and I cannot speak with the same 

 conviction as to primitive and ancestral characters, but there 

 are a few definite points upon which the evidence seems to me 

 more clear. 



Anastomosis of Dorsal Vertebrce. — In pigeons, as in some other 

 groups of birds, there is a marked tendency to anastomosis of 

 some of the dorsal and posterior cervical vertebrae, with the 

 result of giving a greater rigidity to the vertebral column. This 

 anastomosis affects the vertebral centra, the neural arch, and the 

 articular processes, and is the result of ossification of the liga- 

 ments, such as occasionally may be found in old specimens of 

 almost any group. Typically, in pigeons three vertebrae, usually 

 the three anterior dorsals, are anchjlosed in this way ; and I have 

 not yet found in any diastataxic form a greater number of 

 vertebrae affected. But among the eutaxic forms the fusion has 

 proceeded further. In A, «, C, and F it affects four dorsal 

 vertebrae, while in B, D, and E five are united. Similarly, the 

 extent to which the ilia are increased by secondary ossification 

 of the adjoining ligaments and membranes is on the whole more 

 extensive in the eutaxic forms. 



Another point of some little importance in pigeons, as in 

 many other groups of birds, is the degeneration of the fibula. 

 I do not think it can be doubted that a fully formed fibula 

 is a primitive character, while degeneration implies secondary 

 modification. Tnis degeneration is usually accompanied by re- 

 daction of the deep or second peroneal muscle which springs 

 from a varying area of the distal end of the fibula, and which 

 shows special signs of degeneration among eutaxic pigeons. 

 Beddard and Parsons have shown that the absence of this muscle 

 among Parrots is a feature of systematic imjDortance (8). In 

 Pigeons generally the second peroneal is a strong well-develoi^ed 

 muscle, and the ossification of the fibula extends almost to the 

 extreme distal end of the tibia, where it is continued in a strong 

 fibrous band. Among the eutaxic forms, the ossification is never 

 so much as seven-eighths of the length of the tibia, and seldom 

 so much. In A, a, B, C, and D it does not reach more than 

 three quarters of the length of the tibia, and the whole bone is 



LINN. JOUKN. — ZOOLOGY, VOL. XiVII. 17 



