236 



[chap. 



View from above of the Parachordals axd of the Trabe- 

 cule ON the Fifth Day of Incubation. (From Parker.) 



In order to shew this the whole of the upper portion of the 

 head has been sliced away. The cartilaginous portions of the 

 skull are marked with the dark horizontal shading. 



c.v. 1. cerebral vesicles (sliced off). e. eye. nc. notochord. 

 iv. parachordal. 9. foramen for the exit of the ninth nerve. 

 d. cochlea, h.s.c. horizontal semi-circular canal, q. quad- 

 rate. 5. notch for the passage of the fifth nerve. Ig. ex- 

 panded anterior end of the parachordals, pt.s. pituitary 

 space, tr. trabeculse. The reference line tr has accidentally 

 been made to end a little short of the cartilage. 



(2) A pair of bars forming the floor for the fore- 

 brain, and known as the trabeculce (tr.). These bars are 

 continued forward from the parachordals, with which, in 

 the chick, thev ai"e from the first continuous. United 



