454 Illinois State Laboratory of Natural History. 



hypodermis of XI is slightly modified. The prostomium and 

 anterior somite are very sensitive and thin-walled, and at the 

 slightest irritation are so retracted that the first setigerous 

 somite seems to form the end of the worm. 



The brain is concave posteriorly, and its anterior part is 

 prolonged into a process on each side of the median line. 

 The alimentary tract has no special features distinguishing it 

 from other Tubijicidce. The pharynx occupies somite II and 

 part of III ; the wall of the dorsal side is somewhat thicker 

 than that of the ventral side ; the transition from the oesoph- 

 agus to the intestine is gradual ; and chlorogogue cells 

 appear rather abruptly in the anterior part of VI. The inner 

 epithelium becomes like that of the intestine in the posterior 

 part of VI, while the diameter of the alimentary tract becomes 

 considerably enlarged in VII. Posterior to this somite there 

 is no great change in the diameter of the intestine or in the 

 character'of its walls. The coelomic corpuscles are very few 

 in number and of irregular form. 



The circulatory system cannot be studied in the living 

 specimens, and it has proved an especially difficult task to 

 work out its anatomy from sections. One pair of " hearts " 

 is present in VIII, and in one specimen examined there were 

 additional lateral vessels nearly as large in IX. The "hearts" 

 communicate with the dorsal vessel, and no traces of a 

 supra- or sub-intestinal vessel have been found. Anterior 

 and posterior to the region of the reproductive organs the 

 alimentary tract is invested by an extensive system of blood 

 sinuses connected by a median ventral sinus or vessel, which, 

 however, seems to have no direct connection with the ventral 

 vessel nor to have the relations of a sub-intestinal vessel. 



Paired nephridia are present in VII-IX, wanting in X-XIII, 

 and begin again in XIV. The nephridiopores are in line with 

 the ventral setae and a short distance in front of them. 



The reproductive organs are similar in structure and 

 arrangement to those of many other Tubijicidce. The testes, 

 spermatheca j , and spermiducal funnels arc in X, and the 

 ovaries, sperm-ducts, and spermiducal glands in XI, on 

 which somite are the spermiducal pores. The sperm-duct 



