44 WESLEY R. COE. 



larger than Nectonemertes the number of eggs produced is at 

 least a hundred times greater than in the latter. 



In all the bathypelagic forms the gonads of both sexes are 

 reduced in number and size to but a small fraction of those of 

 littoral species. A comparison of the forms hitherto described 

 with respect to these structures will show a graded series leading 

 to the extreme condition found in Paradinonemertes in which 

 the male is provided with but two pairs of spermaries (Fig. 

 17 sp). 



In all the bathypelagic forms moreover the spermaries are 

 limited to the anterior regions of the body, and indeed in most 

 species are far removed from their primitive position to the region 

 of the head. In a few forms they are even limited to the area 

 in front of the brain, where they are crowded into a dense cluster 

 on each side of the head, with their sperm ducts opening near 

 the lateral borders of the mouth. 



In the female the ovaries remain in all species in their primitive 

 interdiverticular positions, but as the number of intestinal di- 

 verticula becomes reduced the ovaries surfer a corresponding 

 reduction. The extreme limit in the species known at present 

 appears to be four or five pairs, which number occurs typically 

 in Pelagonemertes rollestoni. 



i. Planktonemertes. In Planktonemertes occurs one of the first 

 steps in the process of reduction. Strangely enough, however, 

 of the several species of this genus thus far described only the 

 females are known with the exception of the single specimen of 

 P. alberti, in which Joubin (1906) clearly shows the two groups 

 of spermaries behind the brain. This investigator did not, 

 however, suspect their true nature. Fortunately an excep- 

 tionally well preserved specimen of P. agassizii has recently 

 come into my hands which proves to be a sexually mature male. 

 This was collected by the U. S. Fish Commission Steamer 

 Albatross from near the equator in longitude 81 West; that is, 

 off the coast of Ecuador. A study of this specimen reveals 

 nine rounded spermaries on one side and eleven on the other, 

 situated immediately back of the brain, medially to the lateral 

 nerves, and laterally to the pylorus (Fig. 3, sp). These sper- 

 maries presumably represent the anterior interdiverticular gonads 



