12 J. PARSONS SCHAEFFER 



also shows some irregularities and lateral buds from the main 

 cords. These may account for the very common diverticula 

 of the adult nasolacrimal ducts (fig. 30). Finally the series shows 

 that the lacrimal ducts (lachrymal canaliculi) begin as sprouts 

 from the ocular end of the mother cord of cells. Both the supe- 

 rior and inferior lacrimal ducts are about equally advanced in 

 development, but neither of them have progressed far enough to 

 reach the free borders of the eyelids and thus establish the defini- 

 tive connections between the anlages of the nasolacrimal passages 

 and the epidermis. 



The lacrimal ducts are also solid cords of cells and show no 

 evidence of lumen formation. In this series (figs. 10 and 11) 

 it would indeed be difficult to say which of the lacrimal ducts 

 (superior or inferior) was the first to begin its budding from the 

 mother cord. Presumably they started budding approximately 

 at the same time. 



So far as my observations would prove there is considerable 

 variation in the development of the lacrimal ducts, notwithstand- 

 ing that both ducts begin, I believe, as buds from the mother 

 cords of cells. The two ducts do not always begin their devel- 

 opment at the same time. If they do begin at the same time 

 then one or the other is often relatively tardy in its growth. 



In figs. 12 and 13 are represented frontal sections through the 

 nasal cavity of a forty-two to forty-five day embryo. On the 

 left side of this embryo (figs. 12 and 13) the superior lacrimal 

 duct is well advanced, almost reaching to the free border of the 

 eyelid. The inferior lacrimal duct on the other hand is extremely 

 backward in its development. The only structure present — a 

 small lateral bud from the mother cord of cells, that may be the 

 beginning of the inferior lacrimal duct, is shown in fig. 12. I, 

 however, am not at all sure that this is the anlage of the inferior 

 duct. It is a well known fact that one or the other lacrimal-duct 

 anlage may fail to reach the free border of the eyelid. It is, 

 therefore, possible, had this embryo (figs. 12 and 13) continued 

 its development to 'term,' that it would have been born without 

 a drainage duct for the inferior eyelid. On the other hand, on 



