CHORIO-ALLAXTOIC GRAFTS. 295 



The cartilages of the nasal capsule of the chick have been de- 

 scribed by Colin i I'jo.v. The prenasal cartilages and the nasal 

 septum an- pre-ent on the eighth day. The primordia of ihe 

 three turbinal> arc- formed. These are the only cartilages which 

 arise from the mesenchyme transplanted in the graft-. 



Graft 41 B i i- a growth of the nasal region . .f a chick of thirty- 

 six hour- of inrnb.i; ion. The graft was removed after -i\ days of 

 growth on tin- chorio-allantoic membrane of the ho-t. a total of 

 ii and one-halt da\ -. and was 3 mm. \ 3 mm. in -i/e. ( )n 

 -ection, the varioti- j. the nasal region are found to be 



present. Tin > compare 1 ,\rably in their development with 

 the normal region in the embryo of eight days of incubation. 



The i;r.ihed dssues with the exception of a portion of tin- ecto- 

 derm are well -u r rou u< led by the mesenchymatous t i in- of the ho- 1 

 membrane. In it. Ion; - areas are definable, the nasal - 



the na-al < a i tin- ltebrain, and the epidermi- of the head. 



With the exi epiion of the epidermis, these have maintained ap- 

 proximately their normal relationships. The section- < nt the 



on transverse!) so that at one end the nasal 

 -epaiat< -d by the cartilage of the nasal septum. As the -cction- 

 an rly, the sacs become surrounded !>\ a < 



tilai^inou- -heath, the prenasal cartilages. As the na-al sacs 

 di-appear | >.~T eri< irlv . the forebrain appears. It i- hea\ily 

 in til (rated \\ it !: bli-.d D 'rpn-ck-s \\hich do not seem t" be located 



in an\ organized vessels Between these structures themseb 



and -epaiatin;^ them from the chorionic and allantoic boi-der- of 

 the lio-t membrane is 1 growth of me-eiich\ me. A more 



detailed de-cri] >t ion . .f these parts follows. 



The na-al sacs are t \\'o in number and di-tinct I Tlu-\ 



end blindly at both ends and an- com pie t el \ -urroundi-d b\ - me-en- 



ch\ me. save at one place where the left -ac retain- it- connection 

 anteriorly \\ith the epidermi- of the he..d. Po-teriorly t lu-\- 

 \\ iden out forming cavities of some size. 1 he epithelium which 

 liiu-- the cavitie- i- columnar in t\|n . Mito-i- i- fairK i ..mnion 

 in the entire region but i- more commonly found near the cephalic 

 border where the epithelium i- noticeably thickened. I'or the 

 nio-i part thi- la\er i- -harply detineil from the -urroundin^ 

 me-ench\ inc. SO that it appear- a- if a membrane were pre-ent 



