PROBOSCIS. 53 



these fibres, in common with others in the organ, present a coarser appearance in transverse 

 section than after hardening in chromic acid. The fifth layer from without inwards is a strong 

 band of circular fibres (e), the circular muscular coat, which forms a counterpoise to the pre- 

 ceding. Within is a basement-layer (Ji) of pale translucent texture, best seen in longitudinal 

 sections (Plate XI, fig. 8), for in transverse cuts the coat is apt to be confounded with the 

 inner layer of circular fibres. It has, on the whole, a homogeneous appearance. Upon this layer 

 rest the peculiar glandular papillae, which arise from a distinct margin on its inner edge (Plate XI, 

 figs. 8 and 9, b). In the ordinary transverse sections of the proboscis these organs form en 

 masse a somewhat foliated or frilled arrangement, often of a very symmetrical appearance. In 

 contracted specimens the entire cavity is filled up by them and their translucent gelatinous 

 mucus. The largest villi or glandular processes (Plate XI, fig. 10) are situated some dis- 

 tance in front of the stylets, for towards this region they become smaller, and finally the 

 fundus is clothed only by minute papillae. Sometimes they present a coarsely fringed appear- 

 ance, with large granules in their interior ; and when the tube has been turned inside out they 

 have a villose aspect, the tough mucus adverted to above projecting in filaments from their 

 surface under the slightest pressure. I have generally observed, also, towards the first portion 

 of the protruded organ, fine motionless processes like cilia jutting from the apices of the 

 glands, and they are probably homologous with the minute spikes which occur on those of 

 the posterior region after rupture from pressure. I do not think, at all events, that they can be 

 called urticating organs. In Tetrastemma the glandular papillae are leaf-shaped, and somewhat 

 crenated at the border, where there is a regular moniliform appearance from the arrangement of 

 the globules (Plate X, figs. 19 and 20). Under pressure, they are granular internally, and fur- 

 nished with numerous globular or wedge-shaped mucous masses that refract the light like oil. 

 The same type of structure is found in the proboscides of Amphiporidae from New Zealand, 

 only the longitudinal bands of the reticulated layer are more numerous than in A. lactifloreus. 



The description just given of the structure of this region differs much from that of 

 M. de Quatrefages, almost the only author who has entered into the minute anatomy of the 

 proboscis in the Enopla. He states, like Mr. H. Goodsir, that externally the tube is supplied 

 with a series of transverse muscular bridles, which maintain it in position within the body of the 

 worm, and he shows a section of the parts in Nemertes balmea, which bears out his description 

 very well ; but he did not observe that, if such bridles existed, they would have to pass through 

 the muscular sheath in which the organ glides, before reaching the body-wall of the animal. 

 His minute anatomy of the proboscis is chiefly taken from the examination of Borlasia anglim, 

 and hence cannot apply in any degree to the Enopla, though he considered it the type of both. 

 He makes only two muscular layers in the wall of this organ, and though in his section from 

 B. anglice he indicates " traces de fibres trans versales," by a few lines crossing these longitudinal 

 coats, he distinctly observes that they are not apparent in the smaller species. The longitudinal 

 fibres are separated, he states, by a transparent homogeneous tissue, which forms a great number 

 of bridles of very elastic fleshy columns, making, in other words, an elastic cellular layer ; and he 

 figures this in the before-mentioned section, adding that this lax cellular arrangement will give the 

 two longitudinal muscular coats that independence of action necessary for the proper performance 

 of their functions. It can only be supposed that he refers to the reticulated layer by this descrip- 

 tion. He mentions a transparent homogeneous coat within his longitudinal muscular layer, cor- 

 responding to the mucous coat of the higher animals, and adds that the papillae of the latter are 



