EYE OF NOTORYGTES TYPHLOPS. 553 



this part, however, is the hirge irregular sac (figs. 1 and 

 2, C.S.), the hinder wall of which is in close contact with the 

 median anterior and antero-lateral part of the pyriform 

 fibrous capsule [f.c.), which is here thinner though more 

 compact than elsewhere. The size of this sac varies as follows : 

 Length (antero-posterior) "7 mm. to '52 mm., vertical diameter 

 '52 mm. to '42 mm., horizontal diameter '42 mm. Into its 

 cavity there open some four to six ducts [l.g.d.) from 

 the large lachrymal gland, while from it anteriorly there 

 pass off two ducts, the small and outer of which (fig. 2, e.d.) 

 runs obliquely outwards and forwards for a variable distance, 

 "31 mm. to "79 mm. long, and ends blindly in the dermis near 

 the skin. In the case of the shorter of these outer ducts the 

 pigment in its Avail is so thick as to obscure its minute struc- 

 ture. The larger and inner of the ducts, however, descends 

 obliquely forwards and inwards, and then passes through a 

 definite opening in the skull wall, which is visible in the 

 dried skull (contra Dr. Stirling [11, p. 162]), near the lachry- 

 mal notch, sometimes higher or lower. 



The sac (c.s.) in front of the eye is lined by somewhat 

 columnar epithelium, continuous with that of the two ducts 

 leading from it, that of the exterior blind duct [e.d.) becoming, 

 however, more cubical and thick-walled in structure. The 

 sac also is covered with a thick layer of circular muscle- 

 fibres, which becomes much thinner both where the sac wall 

 is in contact with the eyeball, aud over that part of the 

 duct outside the skull wall, and is almost lost on that part 

 inside the bone. In both sac and duct there is often to be 

 found a quantity of secretion. The duct then descends 

 from its entrance, as a definite tube through the skull 

 wall, obliquely downwards and forwards close to the wall 

 of the skull in a distinct groove (rarely absent) formed by 

 the angle of the bony floor of the lateral cavity of the 

 nose and its external side wall. It is separated from the 

 olfactory mucous membrane by a more or less developed 

 glandular mass, of which more has been said when dealing 

 with Jacobson's orafan in Part II of these Contributions. In 



