COLUMBA. 375 
half-way along its ventral border. Posterior to it is a 
triangular ¢schiwm with a large oval foramen (the éschiatic 
foramen). From its anterior border there runs backwards 
beside the edge of the ischium a long pudis. There is 
no symphysis. Just above and posterior to the acetabulum 
is a small facet, the axtitvochanter, which articulates with the 
trochanter of the femur. 
The hind-limb has a short femur, a small and vestigial 
fibula, but a large ##bia to which are fused the proximal 
tarsal bones, hence it is known as the “#dzofarsus. This is 
followed by another compound bone, consisting of the 
Fig. 269.—DIAGRAM OF A Fowl’s Ecc aT LAYING. 
(After ALLEN THOMSON.) 
Blastoderm, 
Plug of White Yolk. 
Air-Chamber. 
Outer Egg- 
Membrane 
Inner Egg- 
Membrane. Vitelline Membrane. 
distal tarsals and three metatarsals, which is known as the 
tarsometatarsus. It forks into three processes at its distal 
end, each of which bears a digit. A small bone on its 
inner side is the first metatarsal, which bears the first digit. 
The number of phalanges increases outwards from two to 
five. The pigeon has therefore no fifth or outer toe, and 
the first is opposable to the other three. 
In the hind-limb there can be recognised the same two 
features as in the front-limb, “2, the reduction in the 
number of digits and the fusion of tarsals and metatarsals. 
In the hind-limb there is, however, a further fusion of the 
