THE LATERAL PHARYNGEAL LYMPHATIC 37 



with that of the precardinal vein at points opposite to them, or, 

 with that of any of the more caudally situated anlagen of the 

 lateral pharyngeal lymphatic which do connect with the veins. 



As far as my own observations are concerned, the independent 

 anlagen of the anterior portion of the lateral pharyngeal lym- 

 phatic first appear as small lymph vesicles or lymph sacs which 

 lie often remote from the veins in an otherwise densely arranged 

 and apparently undifferentiated mesenchyme. In later stages, 

 however, the mesenchymal cells which bound these vesicles begin 

 to arrange themselves in a more regular manner and to assume an 

 endothelial form. If it would not lead to confusion, one might 

 speak of these independent anlagen as lymph vesicles before and 

 as lymph sacs after a definite endothelium has been formed. As 

 far as I can determine by the aid of injections and by a study of 

 sections, the independent anlagen of the anterior portion of the 

 lateral pharyngeal lymphatic (between 13 and 1 in figure 10) 

 arise in situ in the mesenchyme independently of any preexisting 

 endothelium, and their mode of development appears to be a rep- 

 lica of that which has been described above for the subocular 

 lymph sacs. 



2. The development of that portion of the lateral pharyngeal 

 lymphatic which lies opposite to the points at which primary 

 communications are established between it and the precardinal 

 (jugular) vein 



We now pass to a consideration of those anlagen of the lateral 

 pharyngeal lymphatic which arise contiguous to the precardinal 

 vein and contiguous to the points at which we know the lym- 

 phatics may establish direct and typical communications with 

 the veins. As stated above, these anlagen are confined to a 

 district which lies between the caudal end of the otocyst and the 

 cardino-Cuvierian junction, and we have seen that much varia- 

 tion also exists as regards the location and number of the com- 

 munications which may be established within this district. The 

 multiplicity of communications which these anlagen may effect 

 with the veins, is apparently analogous to the somewhat similar 



