its lower siae the two kinds of epithelium meet. This projec- 

 tion is noticeable in all my sections of the septa, from this 

 stage onward. It may be due to contraction of the muscles 

 but from its position, its Constance, and the kind of epithe- 

 lium covering it, it seems probable that it is tht rudiment 

 (Anlage) of a gastric filament, i^'ig. 48 shows the histology of 

 this region. The epithelium lining the proboscis and the oral 

 side of the central stomach is composed of moderately deep co- 

 lumnar cells with a dense, granular contents, small nuclei, and 

 indistinct cell walls. Among them there is occasionally a 

 nettle cell. On what I suppose to be a gastric filament, the 

 epithelium is of nearly the same character. Below this, it 

 is very different. Flere the cells are more than twice as 

 deep, are vacuolated,, have larger n.,clei, and the free ends of 

 most of them are filled with coarse granules that stain with 

 safranin and are apparently composed of a secreted substance. 

 VII. The Strobi la. 



Development of tne Rhopalia . 

 When the scy]Dhistoma has reached a diameter of about two 

 millimeters, the first chai'acters appear iJaiat are distinc- 

 tive of the Strobila. The first noticeable change in this 

 direction takes place at the bases of the tentacles of the more 

 erect series. 



40 - 



