38o 



TORREY 



found scattered throughout the column in large numbers, but not in 



definite rows as in the typical Edwardsia. Fig. 8 was drawn from 



a portion of the wall removed from the polyp shown in Plate xxiv, 



fig. 3. The transverse lines are surface wrinkles. The two pairs 



of dotted lines indicate the 

 contours of the bases of two 

 adjacent mesenteries. Only 

 the outlines of the capsules ap- 

 pear. 



Structure. — The three re- 

 gions of the body wall differ in 

 histological structure. The 

 capitulum (fig. 9) possesses no 

 cuticle ; the ectoderm contains 

 numerous gland cells with 

 granular contents, and occa- 

 sional goblet cells ; it is much 

 thicker than the endoderm ; the 

 mesoglcea is comparatively thin. 

 In the scapus the relative thick- 

 ness of ectoderm and endoderm 

 are reversed. Fig. 10 repre- 

 sents a longitudinal section of 



this region. The columnar cells of the ectoderm are much lower than 



those of the endoderm. They are covered by a cuticle in which several 



lamellae can be distinguished and to 



which sand grains, diatom shells and 



other debris adhere. The mesoglcea 



is thick and is thrown into a great 



number of transverse folds on the 



side turned toward the endoderm. 



These folds are covered by a con- 



tinvious layer of circular muscle fibers. 



The endoderm is twice the thickness 



of the ectoderm. In the physa the 



ectoderm is crowded with gland cells, 



which account for its adhesiveness. 



A cuticle is absent. Everywhere in 



the endodorm — in the tentacles, mesenteries, mesenterial filaments, 



and parietal endoderm — there are large gland cells with deeply staining 



granules. 



Fig. 9. Edvjardsiella sipunctiloides. 

 Section through capitulum. 



Fig. 10. Edzvardsiclla sipuncti- 

 loides. Longitudinal section through 

 scapus. 



