SALIVARY GLANDS OF LOWER PRIMATES 105 



laid down as primitive anlages in definite and constant situations and 

 grow thence by further extension and proliferation of the glandular 

 epithehum. 



In regard to the components of the general alveolingual field, the 

 multiple individual glandular elements composing the lesser sublin- 

 gual group proper practically represent a primitive embryonic type 

 of glandular aggregation carried into the adult organization. As a 

 matter of observation these simple and phylogenetically more ancient 

 elements appear relatively late in the ontogeny. The eariier lesser 

 subhngual sprouts have a temporary association with an epithelial 

 keel, which fact is of very pregnant significance in regard to the 

 genetic interpretation of salivary structures (cf. Part IV). The 

 first lesser sublingual anlages develop as sprouts derived at intervals 

 from a continuous lateral epithelial crest of the alveohngual area, 

 the most cranial buds being the earliest in appearance. Later on in 

 development they lose the primitive connection with the crest, and 

 multiple additional members of the group are formed as separate 

 and distinct derivatives from the epithehum of the subhngual phca 

 and lateral area of the alveolingual floor. 



On the other hand, the earliest anlages of the two remaining members 

 of the entire alveolingual group, the submaxillary and greater sub- 

 lingual components, arise in man in connection with the lingual sulcus 

 and the flange derived therefrom. In the human embryo of 20 milli- 

 meters a few epithelial thickenings appear as an intcm'iediate anlage 

 between the Ungual and alveolar sulci. Possibly these structures 

 represent in the human embryo an extremely evanescent intermediate 

 salivary genetic line (primitive greater sublingual) which normally 

 merges into the median submaxillary hne, since the sprouts are no 

 longer found in the human embryo of 22 milhrneters, whereas in some 

 of the lower mammalia (cf. Schulte on ontogeny of Cat and Pig, 

 Parts VI. and VIII) this intermediate or greater sublingual line ap- 

 pears more definitely organized and plays a greater part in the develop- 

 mental evolution of the median alveolingual field. The early individual 

 embryonic anlages may unite into integers of two kinds, differing in 



their final fonn both functionally and structurally from each other : 



I. The submaxillary and greater subhngual anlages give rise at their 

 caudal ends to large epithehal sprouts, and the secretory portions of 



