488 H. F. MOORE. [Vol. X. 



entirely within somite XIII. It consists of a circular disc-shaped 

 mass, prolonged at its free end into a short tail containing the 

 most mature ova. The septum to which it is attached has been 

 thrust backwards by the enormous development of the sperm 

 sacs, until it roofs over the entire length of the ovary, and the 

 cavity of somite XIII is very much reduced. 



The oviduct opens internally upon the anterior face of sep- 

 tum 13-14, being there expanded into a ciliated disc closely 

 adhering to the septum. Near its upper mediad border this 

 disc is invaginated into somite XIV, carrying with it the mus- 

 cular septum. There is thus formed a small globular sac 

 opening into somite XIII, but apparently lying in the succeed- 

 ing somite. It is lined with cubical ciliated cells continuous 

 with the cells of the ciliated disc, and is covered by top-shaped 

 cells derived from the coelomic membrane. Between these 

 two layers lie muscle fibres in two layers at right angles to one 

 another. 



This sac is probably an ovisac, but is similar to none of the 

 published descriptions of that organ in other worms, and it is, 

 moreover, so small that it could not accommodate more than 

 two or three ova at a time. Its interior is undivided by par- 

 titions or trabeculae, and the muscular layer is well supplied 

 with blood vessels. The oviduct passes through septum 13-14, 

 from the lateral ventral border of the ciliated disc, that is, from 

 the portion farthest removed from the ovisac. It is ciliated 

 for its entire length, and has an outer irregular, but mostly 

 circular, layer of muscle and connective tissue fibres continu- 

 ous with the same tissues in the septum and body walls. 

 Blood capillaries lie imbedded in this musculo -connective 

 tissue tunic or between it and the lining layer of columnar 

 ciliated cells. 



For a short distance, after passing through the septum, the 

 walls are thrown into internal longitudinal ridges, principally 

 due to irregularities in the length of the ciliated cells ; at its 

 distal portion, however, it is oval or circular in cross section. 

 Some of the sections showed ova at about the middle of their 

 journey to the exterior. Spermathecae are not present. Al- 

 though the sections were carefully examined, I was unable to 



