662 GERARDA STIASNY-WIJNHOFF 



before the brain. Brinkmann showed in his monograph 

 that this characteristic seems to be a most important fact in 

 the propagation of the species, coinciding with the development 

 of copulatory organs. In this part of the body the pseudomeric 

 arrangement is not so well developed or is even absent as it is 

 in the stomodaeal part, and only the entodermic blind-gut can 

 show metamerically arranged diverticula. In the genera in 

 which testes are known these are arranged in two ways : (1) with 

 a tendency to metamerical arrangement (only behind the brain) 

 in Plotonemertes, Paradinonemertes, Phallonemertes, Chuniella 

 and Dinonemertes, Biirgeriella. Chuniella, with its long 

 irregular rows of testes, seems to be the most primitive ; the 

 influence of the diverticula of the blind-gut is seen here as well 

 as in Biirgeriella, where they lie more irregularly but are less 

 in number. Plotonemertes represents the next stage, and the 

 regularity seems to be perfect in Phallonemertes, Paradino- 

 nemertes, and perhaps in Dinonemertes alberti. 

 (2) In the other group the irregularly placed testes show a ten- 

 dency to discharge the sperm as near to the head as possible 

 and to form clusters. The effect of this arrangement is show'n 

 by Brinkmann. In Nectonemertes with its tentacles the 

 testes lie in two irregular rows behind and at the side of the 

 brain, but long gonoducts have developed (Text-fig. 25) that 

 all point to the head ; they are still more forward and irregular 

 in Armaueria ; in Natonemertes a pair of irregular clusters lies 

 just beneath the brain, and in Para- and Balaenanemertes 

 the clusters lie at the side of and before the brain and have their 

 gonopores all directed to the proximal edge of the body. 

 Pelagonemertes shows the same features as Balaenanemertes. 

 So the gonads of the Pelagica developed quite differently from 

 those of all other Nemerteans. 



The result of the examination of the anatomical features of 

 the Pelagica, the Eeptantia, and Siboganemertes in thlese 

 pages is : 



1. That the division of the Enopla into Polystilifera and 

 IVlonostilifera is well founded, as not only the differences in the 

 armature of the proboscis exist, but also the way in which the 



