EYE OF THE ENGLISH SPARROW 



417 



into two veins (v) at the angles of the folds. These veins flow 

 into a larger vein which extends along the base of the pecten 

 (vb) parallel with the basal artery. The general arrangement of 

 these arteries and veins and their connection with the vessels 

 which pierce the sclerotic is shown in text figures 34 and 35. 

 The artery which supplies the pecten is derived from the oph- 

 thalmo temporal branch of the external ophthalmic artery 

 (fig. 15, p). It pierces the sclera close to the posterior margin 

 of the optic nerve. In its course through the sclera it takes a 

 diagonal direction to reach the center of the base of the pecten. 



Fig. 34 Diagram showing the relations of the optic nerve entrance to the 

 pecten and the basilar artery and vein. Op N, optic nerve; Pect, pecten; PA, 

 basilar artery to pecten which sends a branch along the middle of each fold; 

 Ch, chorioid; PV, basilar vein from pecten which receives a branch from each 

 angle of the folds of the pecten; Ret, retina; Scl, sclera. 



According to Leber ('03), the basilar artery of the pecten cor- 

 responds to the hyaloid artery of mammals; that, in the embry- 

 onic development of the bird, it does not extend out into the 

 vitreous body, but extends along the wall of the eye. I have 

 found this latter statement true in the development of' the spar- 

 row eye. Figure 74, plate 12, represents a section perpendicular 

 to the retina and at right angles to the long axis of the pecten. 

 Here the pectinal artery (A) is shown in cross-section at the 

 exterior, a portion of its course through the sclera, and in cross- 

 section at the base of the pecten. The vein (F) at the base is 



