344 The Philippine Journal of Science lais 



coalesce and run together to form the smooth perisarc of the 

 mature pedicel. 



Coenosarc. — There is very little variation in the ectoderm of 

 the coenosarc, except in the region immediately below the hy- 

 dranths and in the processes of the hydrorhiza used for attaching 

 it to the surface on which it is growing. In the normal coenosarc, 

 the ectoderm is a very thin layer, consisting of flat, 6-sided, or 

 irregular cells averaging 38 by 7 ixfi. These cells seem to be 

 much larger and in a more flourishing condition in the upper 

 part of the pedicel than in the lower portions (Congdon '06). 

 Indeed, sections of the lower portions of pedicels often show 

 a very thin ectoderm from 3.5 to 5 /a/a in thickness, while in 

 the upper regions of the pedicel the ectoderm layer is from 6 

 to 10 jjLfi thick. The ectoderm of the coenosarc as a whole takes 

 a more diffuse and darker stain than the endoderm. The nuclei 

 are small, and the nucleolus when present stains a slight brownish 

 tinge in Delafield's hsematoxylin or safranin. The ectoderm 

 sends out scattered extensions to the perisarc. Some of these 

 extensions contain a central region of mesogloea, but most of 

 them are protoplasmic processes. These are particularly nu- 

 merous near the distal end of young pedicels where the perisarc 

 is being formed from tubes produced by the ectoderm cells. 



The hydranth is joined to the pedicel by a constricted region. 

 Covering this neck and extending below it for some distance and 

 above it to the groove of the sense ring is a region of enlarged, 

 heavily staining, glandular ectodenn, evidently similar to the 

 cambium of Jickili ('82), of Seeliger ('49), and others. The 

 ectoderm of this region consists of cells distinctly different from 

 those of the normal ectoderm. They are large, rough, irregular 

 cells, with their long axes at right angles to the long axis of the 

 stem, filled with pigment granules, and very evidently glandular 

 in their nature. Where eosin or Congo red was used as a plasma 

 stain, these cells were the only ones to take the counterstain, 

 and with Delafield's hsematoxylin they stain a diffuse bluish pink 

 which contrasts with the sharp blue of the endoderm or the more 

 diffuse blue of the other ectoderm cells. Weismann considered 

 the upper portion of this region to belong to the sense ring, but 

 in E. griffini there seems to be no real distinction except in size 

 between the cells of that part of the sense ring below the groove 

 and those of the cambium region; indeed, one joins the other 

 without a break. The maximum thickness of these cells of the 

 lower part of the sense ring or, as seems the more natural ter- 

 minology, the upper part of the cambium region, is 60 fifu 



