70 ANATOMY OF THE ENOPLA. 



bears an " isolated" stylet. He also represents certain lines, which indicate a sheath [cul-de-sac) 

 around the proboscis, a state that has not been seen in our examples. 



g. Review of previous Interpretations of the Proboscis. 



The proboscis was held to be a genital organ by some authors, as Huschke, Quoy and 

 Gaimard, and (Ersted; others, e. g., Ehrenberg, Johnston, De Quatrefages, Williams, Busch, Leidy, 

 Girard, and Stimpson, maintained that it was the digestive canal ; while H. Pathke called it an 

 organ of touch. Some, again, have mistaken it for a parasitic worm, or a Nemertean embryo. 

 Amongst those who have studied its anatomy in the Enopla, M. Ant. Duges considered the organ 

 to be part of the digestive system of his Prostoma armatum. He observed the stylet-sacs and 

 their contents, which he described as six hard transparent points, disposed in two groups, while 

 the central apparatus consisted of a horny oblong piece of a brownish colour. He thought the 

 central organ would pierce the skin of the annelids on which the animal might prey, while the 

 lateral points would retain them captive ; and, moreover, that such an apparatus approached the 

 hooks pertaining to parasitic worms, e. g., Polystomes and Bchinostomes} He sketched rather 

 rudely the structure of the organ in one of his plates, 2 and it is evident he was acquainted with 

 the three regions ; moreover, a sheath for the proboscis is indicated in his drawing. 



In Gaimard's ' Voyages de la Commission Scientifique du Nord, en Scandinavie/ the 

 anatomy of the proboscis in the Enopla is represented with considerable accuracy. The papillary 

 lining of the organ is separated from the external layers. The central stylet, however, is placed 

 far back, and no special floor of the anterior chamber is formed, the apparatus being enveloped in 

 a broad mass of circular or transverse fibres, but the clear muscular investment is definitely 

 figured, and there are longitudinal fibres posteriorly. Over the reservoir spiral fibres are clearly 

 indicated, and the posterior region has at least two coats. Moreover, ducts to the marginal 

 stylet-sacs are shown, and though they are two instead of one in each, yet their presence is thus 

 early indicated. In Plate E, fig. 11 of this work, a single duct proceeds from each marginal 

 stylet-sac, and, after a short course in a direction forward and inward, it divides into two 

 branches, one of which communicates with the floor of the anterior chamber, and the other slants 

 inwards and somewhat backwards to open into the ejaculatory duct. The proboscis is also figured 

 in an extruded condition (Plate E, fig. 15), but the structure of the stylet-region in this position has 

 been erroneously delineated. The artist represents the central granular apparatus and the stylets 

 throughout very fairly. 



The minute anatomy of the organ given by M. de Quatrefages is somewhat inaccurate. I 

 have not observed that the dilatations and contractions of the channels of the reservoir (his 

 oesophagus) vary in the manner he refers to in different species. He describes two swellings of 

 this " oesophagus," a large lozenge-shaped one at its commencement, and another corresponding 

 to our reservoir, these dilatations being connected by a straight channel. The former may have 



i The stylets of the Nemerteans seem to me to have as little analogy or homology with such 

 structures as with the (i crystalline styles " in the stomachs of certain mollusca. 

 2 f Ann. des sc. nat./ l re ser. Zool., torn. 21, pi. ii, f. 5. 



