376 H. H. SWINNERTON. 
It is much to be regretted that Mollier did not make 
careful reconstructions of the developing pectoral skeleton in 
the sturgeon. The study of sections alone cannot give a 
clear idea of the changes in place relations. 
In both salmon and stickleback at the earliest stage the 
glenoid approximates to the most primitive position, viz. 
parallel to the long axis of the body. In the former, as 
development advances, the fin-plate and coracoid region 
rotate, so that the glenoid border slopes obliquely inwards. 
In the latter no such movement takes place, and the glenoid 
line rotates into a vertical position. 
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Fie. 1.—Diagram to illustrate the hypothetical pectoral skeleton of 
a very primitive teleostome. 
Unfortunately, Swirski, in making reconstructions for the 
pike, did not insert the fin plate; nevertheless, examination 
of his figure shows that in it the movements of the glenoid 
line are the same as those in the stickleback. 
We thus have two absolutely divergent tendencies ex- 
hibited by the developing pectoral skeleton of the salmon 
and sturgeon on the one hand, and by the stickleback and 
pike on the other. These find their concisest expression in 
the statement that, whilst both start with the glenoid line in 
practically the same position, in the one it rotates horizontally 
round the pre-axial end, in the other it rotates vertically 
round the post-axial end. The following diagram will serve 
to make the movements clear. 
