163 



as long as the ampulla. Measurements of this duct in a number of 

 specimens show the length to be about 13-15 microns. The pear- 

 shaped ampulla unites with the digestive tract well down on the side 

 of the latter in the posterior part of V, thus bringing the openings of 

 the spermatheca? almost directly opposite each other. The ampulla is 

 6-7 microns long; has a conspicuous lumen; and bears seven globular 

 diverticula, which are arranged in a single whorl. The diverticula 

 differ somewhat in size, but the structural plan is the same in all, and 

 the lumen of each is continuous with the lumen of the ampulla. An 

 examination of a number of sexually immature specimens showed that 

 the spermathecaj are the last of the reproductive organs to attain their 

 complete development. Some of the specimens, with all of the other 

 reproductive organs well developed, had small spermathecas, with the 

 ducts and ampullae well developed but lacking the diverticula, the only 

 indication of their future position being the rounded collar-like 

 shoulder on the ectal end of each ampulla. A later stage in the de- 

 velopment was noted in which the above-mentioned shoulder of the 

 ampulla had begun to show slight divisions and the boundaries of the 

 diverticula were becoming distinct. Intermediate stages showing the 

 transition between the above-described stages were also found. \Vhile 

 no material was available for a study of very early stages in the de- 

 velopment of the spermathecse, it is quite probable that the following 

 order of development obtains: (i) the development of the duct, (2) 

 the development of the ampulla, and (3) the development of the di- 

 verticula. 



Fridericia sima n. sp. 



(PI. XI, Figs. 43^9; PI. XII, Figs. 50, 51) 



Definition. — Length, 15-19 mm. Diameter, 0.45-0.57 mm. 

 Somites, 52-58. Color, whitish with slight tinge of yellow. Pro- 

 stomium prominent and pointed. Dorsal pores begin on VII. Setae 

 of the typical Fridericia type; 4-6 (rarely 7 or 8) setae per bundle in 

 the anterior region; 4 (rarely 5) per bundle in middle region; and 2-3 

 per bundle in the posterior region. Clitellum on XII-%XIII. Brain 

 about twice as long as wide; posterior margin moderately convex, 

 anterior margin very convex and slightly pointed at extremity, lateral 

 margins almost parallel. Peptonephridia simple, unbranched, and con- 

 fined to V. Dorsal vessel arises in XX. Nephridia with well-de- 

 veloped anteseptal and postseptal parts, the latter being longer and 

 slightly larger than the former. The efferent duct arises from the 

 ventral side of the postseptal part about midway of its length; small 

 distinct reservoir present at its ectal opening. Spermiducal funnel 



