48 CHARLES F. W. McCLURE 



this time neither the transudated lymph nor the dye solution 

 which must first enter the tissue spaces, can possibly reach the 

 general systemic circulation by the lymphatics. When a continu- 

 ous lymph flow is established between the periphery and the veins, 

 the dye which is mixed with the lymph is then able to reach all of 

 the tissues by which it is ordinarily stored. In other words, the 

 initiation of the process of ingestion of dye particles by the macro- 

 phages and of their absorption by renal epithelium, appears to be 

 coincident with the establishment of a continuous lymph flow through 

 the lymphatics between the periphery and the veins. 



The dye solution does not appear to gain admission to the tissue 

 spaces of the embryo until a continuous lymph flow is established 

 between the periphery and the veins. If it did, it would mix with 

 the transudated lymph in the tissue spaces and might enter the 

 independent anlages of the head sinuses, or even the anterior 

 lymph-hearts which, even on the fourth day, are in wide open 

 communication with the veins. Prior to the establishment of a 

 continuous lymph flow from the periphery to the veins, no dye has 

 thus far been observed in any of the lymphatic anlages or in any 

 tissue of the body. 



The amount of dye which reaches the venous circulation by the 

 lymphatics from the tissue spaces, must be directly related to the 

 available lymphatic pathways developed at a given time. When 

 a continuous lymph flow from the periphery is first established in 

 the embryo the amount of dye which reaches the general circula- 

 tion must be relatively small and its action on the tissues corre- 

 spondingly slight. As the amount of dye which reaches the venous 

 circulation necessarily increases progressively with the develop- 

 ment of available pathways, its ingestion or absorption by the 

 typical cells, as the case may be, is gradually hastened up to the 

 time all of the lymphatics are formed. At such a time, as in the 

 case of advanced larvae, the storage of dye granules may then even 

 be accomplished in some cases within twenty-four hours (Exp. 6, 

 7, 11 and 12). 



While under the conditions of the above experiments (Exp. 1, 

 2 and 3) dye granules ordinarily make their first appearance in the 

 cytoplasm of the cell on the ninth day after fertilization, their 



