152 EMBEYOLOGY OF THE LOWEE VEETEBEATES oh. 



wards of the communication between olfactory and buccal cavities, 

 a process which reaches its extreme in the Crocodilia where the palate 

 extends back to about the level of the glottis. 



Stomodaeal Glands. — Whereas in the majority of Fishes the 

 stomodaeal lining possesses only isolated gland-cells, in the air- 

 breathers on the other hand there are developed definite multicellular 

 glands. These originate as a rule from solid down-growths of the 



Fig. 85. — View of the roof of the mouth in three species of Lizard (A, Ege.rnia Kinc/ii ; 

 B, Mabuia quinquetaeniata ; C, Lygosoma rufescens), illustrating the shifting back of 

 the communication between nose and mouth. (After Voeltzkow, 1899.) 



elt, recess into which primitive posterior nares open ; pal, palatine ; jit, pterygoid ; 

 tr, transverse bone; vo, vomer. 



lining epithelium which develop a cavity secondarily. In Urodeles 

 there is, as already mentioned, a special aggregation of these glands 

 forming the gland-field in front of the tongue, while a single gland of 

 considerable size develops from the roof of the mouth in the region 

 between the olfactory sacs (Intermaxillary or internasal gland). 



In terrestrial Eeptiles glands are present in numbers on the roof 

 of the mouth (Palatine), beneath the tongue on each side of the 

 middle line (Sublingual) and along the edge of the mouth just 

 external to the row of teeth (Labial). The poison glands are 

 specialized and enlarged labial glands of the upper jaw except in 



