248 THE FIFTH DAY. [CHAP. 



deepening nasal grooves, and are sometimes spoken of 

 as the inner nasal processes. The outer margin of each 

 nasal groove is raised up into a projection frequently 

 spoken of as the outer nasal process, which runs down- 

 wards to join the superior maxillary process, from which 

 however it is separated by a shallow depression. This 

 depression, which runs nearly horizontally outwards 

 towards the eyeball, is known as the lacrymal groove 

 (see p. 155). 



On the fifth day the inner nasal processes, or lower 

 and outer corners of the fronto-nasal process, arching 

 over, unite on each side with the superior maxillary 

 processes. (Compare Fig. 81, which, however, is a view 

 of the head of a chick of the sixth day.) In this way 

 each nasal groove is converted into a canal, which leads 



FIG. 81. 



HEAD OF A CHICK AT THE SIXTH DAY FROM BELOW. (From 

 Huxley.) 



la. cerebral vesicles, a. eye, in which the remains of the choroid 

 slit can still be seen. g. nasal pits. k. fronto-nasal process. 

 1. superior maxillary process. 1. inferior maxillary process 



