547 



INTERNAI, CHARACTKRS 



The alimentary tract is similar in its parts and relations to those 

 of other species of llclodrilus. The esophagus is of relatively small 

 diameter in \-IX. The calciferous gland involves that part of the 

 esophagus which is in X-^ XIV. In X the esoi)hagus ahruptly in- 

 creases in diameter, especially in the frontal plane, and two lateral 

 pouches are formed. In XI and XII the diameter diminishes slightly, 

 and in XIII more rapidly, so that in the posterior part of the latter 

 somite it is again small. The walls of the pouches in X have numer- 

 ous longitudinal folds which are high on the lateral walls and low on 

 the dorsal and ventral walls. These folds arc continuous posteriorly 

 with longitudinal radially arranged partitions which at their inner 

 edges unite with the esophageal epithelium and at their outer edges 

 meet the circular muscular layer of the esophageal wall. These parti- 

 tions extend back to the middle of XIV, being wide in XI and XII, 

 diminishing in width in XIII, and disappearing in the anterior half 

 of XIV. The partitions divide the wide space between the esophageal/ 

 epithelium and outer wall into longitudinal radially arranged cavities 

 which extend from their anterior opening into the lateral pouches in 

 X to their very inconspicuous posterior openings into the lumen of 

 the esophagus in XIV. The cavities receive the secretions from the 

 secretory layers of the partitions, each of which has two such layers 

 and an included blood sinus. The partitions and included cavities are 

 widest in the lateral and narrowest in the dorso-ventral transverse 

 axes of the esophagus, while the esophageal lumen is narr(nvest later- 

 ally. The epithelial layer of the folds in X and of the esophagus in 

 XI— 5^ XIV is ciliated. The calciferous gland of H. zeteki is very 

 similar to that of a considerable number of other species of Helodrilus 

 which have been examined by the writers. The number of partitions 

 in the gland of H. zeteki in the few specimens examined is 60-64, 

 which is a considerably larger number than that found in some species 

 of smaller worms. The crop involves XV and XVI, and the gizzard, 

 XVII and XVIII. Septa VI/VII-XII/XIII are thickened and XIII/ 

 XI V^ and XIV/XV^ are more strongly thickened. 



The spermaries and spermiducal funnels have the usual positions 

 in X and XI and the two sperm ducts of either side unite near XII/ 

 XIII and form a common duct extending just beneath the peritoneal 

 layer to the anterior limit of XV. Rather large masses of gland cells 

 surround the terminal parts of the sperm ducts and encroach on the 

 cavity of XV and on that of either XIV or XVI. There are two 

 pairs of sperm sacs, one pair in XI and one in XII. Those of the 

 latter pair are the larger, and when fully developed tiu-ir dorsal parts 



