38 DEVELOPMENT OF LYMPHATIC SYSTEM, FISHES 



condition presented by the early anlagen of the mammalian 

 jugular lymph sacs. It is therefore evident that the development 

 of these anlagen should, in all probability, follow the same 

 genetic plan as those of the mammalian jugular lymph sac. 



The anlagen of the lateral pharyngeal lymphatic first to make 

 their appearance in the embryo arise in the cardino-Cuvierian 

 district. These anlagen (3'") are shown in figures 1 and 2, 

 which represent reconstructions of the left and right sides, re- 

 spectively, of a fourteen-day steelhead trout embryo. On the 

 left side of the embryo (fig. 1) a single anlage (cardino-Cuvierian 

 lymph sac, 3"'} is present and lies about opposite the cardino- 

 Cuvierian junction. On the right side of the embryo (fig. 2), 

 however, two anlagen (3'") are met with in the cardino-Cuvierian 

 district, one of which lies opposite the cardino-Cuvierian junction 

 and the other slightly anterior to it. 



These anlagen appear as clear areas which are situated in an 

 otherwise densely arranged mesenchyme. Figure 34 represents a 

 transverse section which passes through the anlage on the left 

 side (3'", fig. 1), and through the more anterior of the two an- 

 lagen (3'") present on the right side of the fourteen-day steel- 

 head trout embryo (3'", fig. 2). The anlage on the left side 

 of the embryo (3'", fig. 1) is found in three sections (10 micra 

 each) and that on the right (fig. 2) in one. On the left side of the 

 embryo (right side of figure 34) the anlage (3'") is connected with 

 the precardinal vein (6) by what appears to be a very narrow 

 extension either of the vein or of the sac, and traces of the in- 

 jecta can be observed in the walls of the cardino-Cuvierian 

 lymph sac. On the right side of the embryo (left side of fig. 

 34) the precardinal vein sends out a blind process in the direc- 

 tion of the sac but does not communicate or connect with it. 

 The more posterior of the two anlagen present on the right side 

 of the embryo (3 A// , figs. 2 and 35) lies free in the mesenchyme, 

 and no observable connection or communication exists between 

 it and the precardinal vein. The conditions observed in this 

 fourteen-day embryo would indicate that the cardino-Cuvierian 

 lymph sacs of the trout are not invariably connected with the veins 

 at the time of their inception. This is a feature of primary 



