316 Elliot R. Downing, 



show that the fats, if absorbed by the endoderm cells in qnantitj^, 

 are promptly altered by them to some other substance. Specimens 

 of H. fusca have been variously fed. some on tiny fish others on 

 DapJinia, on Chironomiis larvae etc. Then at varying times during 

 the digestive process, from fifteen minutes to several hours, the 

 animals have been teased up and the tissues tested or else they 

 have been killed, sectioned and mounted for study. Such studies 

 have shown that while much fat, staining with Sudan III, is liberated 

 in the body cavity as a result of the digestive process, the endoderm 

 cells rarely contain any. Plastids of these endoderm cells contain 

 quantities of brown granules near their inner ends which do not 

 stain with osmic (Fig. 10, Plate 11): towards the ends adjacent to 

 the mesogloea, however, the contained granules do stain with osmic, 

 do not stain with Sudan III and do not show the lecithin reactions; 

 these two sorts of granules sometimes appear in the same plastid. 

 The second sort of granule is prevalent in the ectoderm cells and 

 is found absorbed in the growing eggs and by the interstitial cells. 

 By these, I believe, it is changed to lecithin and stored by the egg 

 in the form of yolk and by the interstitial cell in its nucleus. The 

 nuclei of interstitial cells about to be ingested by the egg sometimes 

 give the lecithin reaction, at times they do not. Those interstitial 

 cells whose nuclei are breaking up into granules preparatory to 

 being ingested show the lecithin test but slightly if at all. It seems 

 a safe inference, then, that if the interstitial cell has altered its 

 nucleo-proteids to the form of lecithin the cell is ingested whole, 

 otherwise it is first disintegrated and the completion of their trans- 

 formation to lecithin is carried on in the egg. The granules of 

 nutritive material absorbed by the egg seem to aggregate in tiny 

 masses contained in drops of highly refractive fluid (Fig. 3); the 

 granules disappear, the drop becomes impregnated with lecithin: 

 adjacent lecithin droplets fuse and the pseudocells are present. The 

 good sized pseudocells are 12 or 14 fi in diameter, some with a 

 nucleolus, others without (Fig. 6, Plate 11). The exact chemical 

 history of their genesis can not be given for want of sufficient 

 microchemical tests and we must be satisfied, temporarily, with the 

 fragmentary account given above. 



20. While Kleixenbeeg found, in H. viridis, that the growth of 

 the ovary ceased with the appearance of the egg, in H. dioecia the 

 interstitials continue to multiply, the ovary continues to increase in 



