20 CHARLES F. W. McCLURE 



6) After remaining fifteen hours and forty minutes in the dye 

 solution, the liver and mesonephros were removed from the body 

 of two other individuals chosen at random, in which no indication 

 of dye granules could be observed in the lymphatics of the caudal 

 fin. A study of sections showed that a trace of dye had been 

 stored in the stellate cells of the liver in one individual, and that 

 no dye had been stored in the liver of the other. It was also 

 found that no dye had been stored in the epithelium of the meso- 

 nephric tubules in either larvae. In both larvae, however, mono- 

 nuclears containing dye granules were found in the liver capil- 

 laries and in the intertubular tissue of the kidneys. 



Experiments 6 and 7 show when an advanced stage of larval 

 development has been reached, that the storage of dye granules 

 in the cytoplasm of typical cells no longer becomes a question of 

 days, but may be accomplished in a relatively few hours. This 

 bears out the view previously expressed, that the prolongation of 

 the ingestion process at the critical ontogenetic stage, at which 

 dye granules are ordinarily first observed, is probably due to the 

 circumstance that developmental conditions are less favorable 

 for rapid ingestion at this time, than at a more advanged age 

 (Exp. 5). 



'These experiments would therefore seem to confirm the view 

 that the initiation of the process by which dye granules are stored 

 in the cytoplasm of certain cells is associated with the attainment 

 of a distinctive ontogenetic larval stage. Experiment has shown 

 that tissues do not react toward these dyes until this stage is 

 reached, irrespective of the length of time larvae may remain in 

 dye before this time. 



These experiments also show that the mononuclear leucocytes 

 may store the dye prior to all other typical tissues, and that the 

 endothelium of the lymphatics of the caudal fin may even store 

 the dye before the epithelium of the mesonephric tubules or the 

 stellate cells of the liver capillaries. It is needless to state and, 

 as experiment shows, if these same larvae had remained a slightly 

 longer time in the dye, the storage of dye granules by the typical 

 tissues would have been still more extensive. See Experiments 

 8 band 11. 



