Postlarval Development of Leucosolenia variabilis, H. sp. 45 



FIG. 2. Larva of second day. 



short, granular cells are formed during larval life by modification of 

 ciliated cells, the intermediate cells being a stage in this process. 



Sections of larvae confirm and amplify the results obtained from a 

 study of the living object (fig. 3). The inner portion of each ciliated 

 cell, which in life appeared refractile, is seen to contain a series of 

 vacuole-like structures, containing granular masses suspended in 

 their interior. At the junction between the internal vacuolated and 

 external granular portions of the cell is situated the opaque and 

 deeply staining nucleus, which has a form like an onion, and is con- 

 tinued externally into the flagellum. Often the inner side of the 

 nucleus is indented by the vacuole beneath it, sometimes to such an 

 extent that the nucleus has the form of a crescent in section. The 

 intermediate cells are very distinct in sections, and by some methods 

 of preservation and staining, e.g., osmic acid followed by picrocarmine, 

 their protoplasm takes up the stain in a remarkable manner, so that 

 larvae treated in this way appear to have a brightly coloured equatorial 

 zone. They lack the vacuolated inner portion, characteristic of the 



