PROBOSCIS. 73 



apparatus to hang therein, apparently by its anterior end. He has mistaken the translucent 

 wedge-shaped investment of the organ for a cavity, and the triangular muscular structure to the 

 exterior is imperfectly figured. He correctly observed the presence of a duct to each marginal 

 sac ; but supposed that these pouches were for the lodgement of stylets discarded from the 

 central organ, and hence saw no connection between the clear globule and the developing 

 spikes therein. His representation of the muscular fibres of the stylet-region is faulty. He 

 discovered the presence of a liquid containing minute granules in the reservoir, and stated that 

 the latter communicated with the " Trompe" by means of an efferent canal ; but he fell into the 

 error of regarding the posterior chamber of the proboscis as a " muscle retracteur." His deli- 

 neation of the opening of the ejaculatory duct is inaccurate, from the absence of the muscular 

 cavity behind the floor of the anterior chamber. The reservoir is regarded as a poison-gland, 

 which squirts its contents along the ejaculatory duct into the wounds inflicted by the stylet. In 

 his more recent e Beobachtungen ' he exhibits the structure of the region in Prosorhochmus 

 Claparedii, but gives no details of the anatomy of the muscles. The central stylet and its 

 apparatus are placed in the middle of a continuous and apparently homogeneous body, the wedge- 

 shaped envelopment of the basal organ and the muscular cavity in front being confounded. The 

 opening of the ejaculatory duct of the " poison-gland" (reservoir) has the same position as in his 

 previous figure, viz., at some distance from the stylet, and passing directly into the floor of the 

 anterior division. He now refers to the posterior chamber, which, he says, occupies the centre 

 of the muscle of the organ, a modified but unsatisfactory "description. The external granular 

 glands are not characteristically figured. 



In his anatomy of the region in Folia ohscura (a Tetrastemma) , M. van Beneden represents 

 no ducts to the marginal stylet-sacs, and no ejaculatory duct. The reservoir has a cavity in the 

 centre, but is likewise furnished with two hypothetical oval vesicles or spaces j while the muscular 

 structure, the floor or ending of the anterior chamber, and other important points, are absent. 

 The statement, that the marginal sacs contained stylets of a smaller size than the central, 

 and of a different form at the base, is also ambiguous. He calls the former sacs pouches of 

 replacement. While he asserts that the proboscis is enclosed in a separate sheath, he distinctly 

 adds, that its muscular retractor is attached to the skin of the animal posteriorly ; and that there 

 may be no misunderstanding, he repeats the statement when drawing up his conclusions, by 

 averring that the internal surface of the proboscis is ciliated, and that it is fixed to the bottom of 

 the digestive tube by a retractor muscle, like the stomach of the Bryozoa. 



So far as they go, Prof. Keferstein's remarks on this region in Folia mandilla {A. lactijloreus) 

 are in advance of his predecessors. He does not mention, however, the minute glands on the 

 floor of the anterior chamber, and represents the aperture for the central stylet much too large, 

 so that in extrusion the muscular space (e in our figures) becomes obliterated. The invest- 

 ment of the granular basal apparatus is continued too far forward in his drawing. He indicates 

 no oblique fibres from the pit of the anterior division, is unaware of the complex 

 anatomy of the proper stylet-region, and represents the coat of the reservoir as composed 

 of longitudinal fibres. The external granular glands are not distinctly described; and 

 the disproportion between the central and marginal stylets is so great, that probably some slip 

 has occurred in their delineation. Lastly, his crenated border (external elastic coat) does not 

 pass the constriction between the proper stylet-region and the reservoir, whereas both this and 

 the longitudinal coat beneath are really continued some distance on the latter. His representa- 

 tion of the extruded organ is also much in need of amendment. 



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