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bulletin: museum of comparative zoology. 



There are commonly but two of these pouches, each containing 

 usually one to three stylets each, although in A. iinparisjnnosus there 

 are three pouches, in A. birnaculatus either two or four, and in 

 Paranemertes calif ornica (Text-figs. 11, 41) four or six, while A. 

 formidabilis has eight or twelve such pouches (PL 17, fig. 102 ; 

 Text-fig. 13). In some forms also there may be five to seven or 

 more stylets in each pouch. Usually at least one of the stylets in 

 each pouch is in process of formation and is surrounded by an oval 



vesicle of clear fiuid. The central 

 stylet, on the other hand, is never 

 found in an immature condition, so 

 that it has been thought that the 

 stylets are formed only in the acces- 

 sory pouches. Here, according to 

 Biirger, each pouch represents a sin- 

 gle cell in which the stylets appar- 

 ently form as concretions in the same 

 way that numerous rhabdites are 

 formed in a single cell. In Carci- 

 NON EMERIES, howcvcr, where acces- 

 sory stylets are wanting, it is certain 

 that the central stylet is formed in 

 situ, and the development of this 

 structure in Geonembrtes strongly 

 indicates that it is qiiite independent 

 of the accessory stylets. It is very 

 doubtful whether the central stylet 

 can, if injured, be replaced by an 

 accessory stylet. It seems far more 

 probable that the central stylet has 

 , ,. . .^ ,w no genetic relation with any of the 



Fig. 13. — AmpJupoms jormidabihs. &> '' 



Outline of stylet apparatus of pro- aCCCSSOry StyletS. 



boscis, with eight pouches of acces- j^^ DRErANOPHORUs the armature 



sory stylets. i i • 



consists of a long, sickle-shaped basis 

 on which are imbedded upwards of 15 to 20 minute, top-shaped 

 stylets. There are also about the same number of pouches contain- 

 ing accessory stylets of similar form. The total number of such 

 accessory stylets may amount to upward of 200 in certain species of 

 the genus. 



