164 OTTO FREDERIC KAMPMEIER 



scheiin's "Vergleichende Anatomie der Wirbeltiere," or to his 

 original article which depicts such a condition in a frog tadpole. 

 An enormous lymph sinus, probably tantamount to the several 

 cephalic subcutaneous sacs of the adult, is seen to occupy almost 

 entirely the ventral and lateral territory of the head. On each 

 side this reservoir passes backward as a short slender duct which 

 opens into the anterior lymph heart, situated in the region of the 

 fore-limb bud. A second set of vessels, draining the posterior 

 portions of the body, unite cranially to form a single trunk, which 

 communicates with the duct coming from the head at its point 

 of entrance into the lymph heart. Besides the chief systemic 

 vessels, numerous smaller subsidiary channels and plexuses 

 spring from them ; but these will not be considered in the present 

 paper and may therefore be disregarded. 



The inception of the large ventral cephalic lymph sinus will 

 be discussed fully, for in the writer's opinion it offers a very 

 clear case of the derivation of lymphatic endothelium from the 

 lining of blood vascular channels. This lymph vessel is an 

 especially favorable object for stud}^ not only on account of its 

 size, but because it originates in the immediate vicinity of veins 

 located in a broad uninterrupted expanse of mesenchyme which 

 is loosely woven yet sufficiently abundant in number of cells 

 to facilitate an examination and comparison of the role played 

 by these structures during the formation of it. Figure 1, inserted 

 for the purpose of orientation, represents a cross-section of the 

 head of an 11 mm. embryo and illustrates the situation of this 

 resevoir (l.) relative to other organs. The position also of the 

 external jugulars (j.d. and j.s.y should be carefully noted, for 

 the five succeeding plates portray events that take place proxi- 

 mately around these veins. Beginning with the stage of the 

 almost completed lymph sinus, the territory ventral to the mouth 

 cavity (m.c.) in consecutively younger embryos was scrutinized 

 with the oil immersion lens. The important revelations are set 

 forth in the camera lucida sketclies reproduced on plates 1 to 6 

 inclusive. To duplicate as nearly as is feasible the course by 

 which the data were obtained, the descriptions commence with 



3 Goette called the external jugular (Gruby and Ecker) the inferior jugular. 



