102 PROF. MARSHALL AND MR. SPENCER. 



nerves of the two sides are still directly continuous with one another ; 

 there is as yet no trace of the secondary root of the seventh. 



At stage k the fifth nerve (fig. 4) has completely lost its primary 

 root and is now attached to the brain by the secondary root alone 

 (a (3) ; a slight trace of the former is still present as a small dorsal 

 projection on the nerve just beyond the root of attachment. Towards 

 the close of stage K, the tertiary or anterior roots have appeared, 

 arising almost certainly as outgrowths of the ganglion towards the 

 brain ; but whether these are altogether new developments or merely 

 new attachments of the primary root is uncertain. The seventh nerve 

 (fig. 3) is in the same condition as the fifth at the preceding stage ; it 

 is now attached by both primary and secondary roots, the former, 

 owing to the growth of the brain-roof, being widely separate from one 

 another. 



At stage n the condition of the roots is much the same as at the 

 end of stage k. The fifth nerve (figs. 5 and 11) is attached by its 

 secondary and tertiary roots, the latter being very constantly two in 

 number, of which the anterior is the larger and attached to the brain 

 some distance in front of the secondary root (v j3). The seventh nerve 

 (figs 6, 11 and 12) is attached by both primary and secondary roots, 

 the nerve between the two being in contact, but not in connection, 

 with the brain ; the secondary root (fig. 11) is divided into an anterior 

 or facial, and a posterior or auditory division. 



At stage o (figs 8 and 9) the chief differences are — firstly, that, owing 

 to increased growth of the brain, the distance between the primary and 

 secondary roots of the seventh nerve is much greater than before ; 

 secondly, that the roots of the fifth and seventh nerves, which from 

 the first have been quite independent of one another, are now situated 

 much closer together than they were at the earlier stages. 



At stage o-p (fig. 14) the two roots of the seventh (vn a and vn /3) 

 are still further apart from one another, but are now very close to 

 those of the fifth. The connection between the two nerves which we 

 have already seen is fully established at stage k, and which is shown 

 at stage l in fig. 10 (N.c.) and at stage n in fig. 11 (N'.c'.) is, by stage 

 o-P, very much more extensive and intimate than previously. The 

 roots of the nerves are still quite distinct from one another (fig. 14), 

 but immediately beyond these roots the two nerves become so closely 

 and extensively united together that it is impossible to draw a line of 

 separation between them. The connection is rendered still more 



