DEVELOPMENT OF SALIVARY GLANDS IN THE DOMESTIC CAT 229 



occupies the axis of an incipient fold, wliile in the following sections 

 (Figs. 51, 52) the fold is reduced to a flange with a pale axial streak 

 and indented at its base by a minimal fissure. Such appearances are 

 characteristic of the cranial end of the anlage up to the stage shown in 

 the 20 millimeter embryo. If the sections are read in a craniocaudal 

 direction, they show a fold gradually compressed to a flange and gradu- 

 ally increasing in width, to which, finally, a sprout is added at the free 

 margin. An anlage Hke this repeats the stages of the ontogenetic 

 process in its several segments. The inference is, therefore, that the 

 earlier phases of the process are still active and are progressive along 

 the buccal sulcus craniad, that the fold of the parotid continues to 

 extend after the estabhshment of the bud, and that, consequently, the 

 definitive duct will be attached to the mouth at a point craniad of its 

 origin. On the left side there is a departure from this t\-pe of anlage, 

 which may be mentioned in passing as it forms the inception of a 

 frequent and important variant. As far as the bud the flange 

 resembles that of the right side. In this section, however, the inter- 

 mediate portion of the flange is not flat, but thickened and circular in 

 outline (Figs. 34, 17, 36, 40). An additional center of prolifera- 

 tion lias appeared and is separated partially, both from the parotid 

 and the buccal sulcus, by minute furrows. The sprout does not in 

 this embryo project freely into the mesenchyme. This is the earliest 

 example of the orbitoparotid element in our series. Caudal to it 

 the flange subsides abruptly. 



In embryos of 14 millimeters the sprout of the parotid begins to 

 grow distad into the mesenchyme. In embryo No. 211 (Fig. 41) 

 this growth is but barely initiated; only in two sections (27 fi) is 

 the sprout free from the oral epithelium. In embryo No. 127 (Fig. 

 43) the sprout is longer and slightly enlarged at its extremity. It is 

 directed from the free angle of the flange ventrad, slightly caudad 

 and laterad, a direction determined for it, first, by the ventrolateral in- 

 clination of the flange itself and, second, by the relation of the mas- 

 seter before alluded to. In this anlage, again, the orbitoparotid 

 variant makes its appearance (77). A model of a parotid, in which 

 the free growth of a sprout is on the point of beginning, is shown in 

 Fig. 95. The flange is triangular; its intermediate portion is much 

 compressed both on its dorsal and on its ventral aspect ; at the free 



