DEVELOPMENT OF SALIVARY GLANDS IN THE DOMESTIC CAT 1 99 



arches. Gegenbauer ' has argued from the occurrence of an isolated 

 cartihige in this situation in Heptanchus that here an element of the 

 visceral skeleton has been suppressed in the interest of freer movement 

 of the jaws. The proportional contribution of the tuberculum im- 

 par is insignificant, merely a median strip along the dorsum of the 

 tongue. 



The embryos of 11.5 miUimeters to 13.5 millimeters show a pro- 

 gressive enlargement and increasing intimacy of contact on the part 

 of the tongue and palate processes, which in the older embryos of 

 tliis period ha\'e come to interlock like a mortise and tenon, while the 

 roof and floor of the mouth become accurately coapted to one another 

 and the cavity is gradually reduced to a slit. Only craniad as the 

 plane of the anguh oris is approached do the dorsal and ventral walls 

 retain any independence of relief. The 11. 5 miUimeter embryo 

 (Figs. 12-14) and that of 12.5 millimeters (Figs. 15-17) show inter- 

 mediate stages; in the 13.5 millimeter embryo the process has attained 

 completion (Figs. 36-39). 



The mouth is now divided into three portions, a medial circum- 

 .lingual cavity and two lateral or marginal regions (Mittelraum oder 

 Gaumenrinne and Kaunishe of Aulmann).^ These regions are con- 

 tinuous at the ventral border of the palate process, the region of 

 junction forming a trough or gutter concave ventrally (Figs. 36-39), 

 which evidently corresponds to the shallow concavity beside the 

 lateral tongue swellings of earlier embryos (Figs. 10, 20). This portion 

 of the mouth subsequently furnishes from its ventral epithelium the 

 material for the anlages of the submaxillary, greater subhngual, and 

 lesser sublingual glands. On account of its importance from this 

 standpoint, it is convenient to recognize it as a region of the oral 

 cavity distinct from, and intercalated between, the circumhngual 

 and marginal cavities. It may be termed the akcoliitgual region; 

 its floor the alveolingual fold or gutter. Here a departure is made 

 from the terminology of Chievitz, which, to avoid confusion, had 

 better be stated expHcitly. Chievitz terms the whole region the 



'Gegenbauer, Carl. iSgS. Vergleichende Anatoraie der Wirbclthiere mit Bertick- 

 sichtigung der Wirbellosen. Leipzig. 



^.\ulmann, G. iqoq. Die Mundrachenvvand der Vogel imd Sauger. Morph. 

 Jahrb. XXXIX. Leipzig. 



