BRITISH NEMERTEANS, AND SOME NEW BRITISH ANNELIDS. 343 



Dr Johnston's* description of the stylet-region is as follows : — " First, we 

 perceive on each side a small circular spot or cavity, in each of which are three 

 spines with their sharp points directed outwards ; beneath these there is a cup- 

 shaped organ encircled above with a faintly plaited membrane, and armed in the 

 centre with a strong spine, which can be compared to nothing more aptly than a 

 cobbler's awl in miniature, the part representing the handle being very dark, and 

 the point transparent and crystalline. This apparatus is placed within the intes- 

 tine, is visible only when this is compressed, and is, as I believe, stomachial, 

 having some distant analogy with the proper digestive organs of Laplysia and 

 Bulla." His anatomy is thus imperfect, and he, moreover, considered that the 

 " intestine," as he termed the organ, proceeded to the tip of the body and termi- 

 nated in a distinct anus. 



Dr Williamsj observes with regard to the proboscis (his alimentary organ), 

 " The extremity of this organ is armed with several styleted jaws, which, from 

 their construction, seem only designed to fix the suctorial end by perforating the 

 alimentary object. When the proboscis is withdrawn into the interior of the 

 body, fitting admirably into a short oesophagus, these sharp instruments are 

 packed and folded upon themselves," the sides of the tubes closing round them. 

 The correct examination of a single extruded organ would have at once dispelled 

 such notions. His supposition — that the glands in the interior of this structure 

 furnished an important secretion for the digestive process, which secretion was 

 exuded into the "oesophagus" (apparently, judging from his figure, f the pro- 

 boscidian sheath), and thence into the great alimentary organ — rests upon no 

 facts. He is also wrong in stating that the outlet of this organ is situated not 

 far from the cephalic end of the body ; but his remark, that there is no open 

 communication between the oesophageal tube (proboscidian sheath) and the 

 " alimentary caecum " is correct. 



Dr Max S. Schultze, in his account of Tetrastemma obscurum§ gives no 

 definite description of the ending of the proboscis, and figures the central stylet 

 as projecting freely into the cavity. He indicates the presence of the muscular 

 space behind this, but confounds its structure with the wedge-shaped setting of 

 the basal sac, the whole forming, he says, a quadrangular mass. He falls into 

 the same error as M. de Quatrefages and others, in describing the terminal 

 ribands of the organ as attached to the wall of the body. His figure || of the 

 exserted stylet-region is incomplete in detail, for he omitted to notice the ducts 

 of the lateral stylet-sacs, though he regarded the latter as the producers of the 



* Mag. of Zool. and Bot, vol. i. p. 530, 1837, copied into " Catalogue" Brit. Mus. pp. 285-6 



f Report Brit. Assoc. 1851. 



% Op. cit. pi. xi. fig. 64. 



§ Beitrage zur Naturges der Turb. 1851, p. 62, tab. vi. figs. 2-10. 



|| Op. cit. tab. vi. fig. 3. 



