PEOBOSCIS. 103 



In transverse section there is externally an investment (a, Plate XX, fig. 4, and Plate XIX, 

 fig. 8) similar to that in the Enopla, apparently composed of homogeneous elastic tissue, yet 

 showing some granular markings towards its outer border. This coat is tougher than any of 

 the others, and often retains its integrity after they have ruptured. A powerful longitudinal 

 muscular layer (5) lies within the former, its fibres in transverse section having the same histo- 

 logical characters as in the Enopla. At opposite or nearly opposite poles of the circle, however, 

 a remarkable interposition severs the continuity of the layer (as seen at g, g). At one pole, two 

 symmetrical bundles of fibres spring from the succeeding circular belt, and, slanting outwards, 

 cross each other, so as to disconnect the longitudinal coat just mentioned, and for a portion of its 

 circumference wedge it between two bands of circular fibres. The outer or oblique bands of 

 circular fibres become lost in the external coat of the organ. The longitudinal layer (b) is thus 

 diminished to a blunt point on each side of the intersection of these peculiar fibres, and a region 

 is formed externally which is occupied by a special and somewhat lozenge-shaped group of longi- 

 tudinal fibres, through which the dotted line g passes. The longitudinal layer, especially near 

 the wedge-shaped ends (where the fibres are often arranged in a thicker mass in these preparations), 

 is marked in the centre by a faint linear streak, as if composed of two layers, but this does not 

 continue all round, and is not apparent in every specimen, nor in L. gesserensis. At the other 

 pole there is a variation, for it is found that an elongated portion (/) is cut off without apparent 

 intersection, the ends of the great longitudinal coat (&) being widely separated. It generally 

 happens that towards this side the bulging of the contracted organ occurs, and, it may be, such 

 forces the edges of the longitudinal fibres apart, and aids in causing the above appearances ; but 

 it would not account for them all. In contraction this coat is sometimes thrown into a silky belt 

 of regularly waved fibres. Within the longitudinal layer is an equally powerful one of circular 

 fibres (c) which, at opposite poles in the transverse sections, gives off the peculiar oblique bands 

 previously mentioned. A basement-layer (d), better marked in Micrura fusca than in Lineus 

 gesserensis, is situated on the inner surface of the circular coat. There is also present in the 

 former species an incomplete belt of longitudinal fibres (e) within the basement-layer, and which 

 is not evident in the latter. Attached to the inner surface of the basement-layer, or in the latter 

 instance partly to the incomplete longitudinal, is the glandular mucous coat (/), which, from 

 lengthened preservation, has in this case become somewhat altered. The glandular bodies are 

 scattered chiefly towards its inner or free surface. In fresh preparations, i. e. in those made 

 from the organ immediately after extrusion from the living animal, a regularly radiate 

 arrangement of this coat is constantly observed, as if a series of explosions had occurred in the 

 mucous substance so as to scatter the globules and gelatinous bands in a fan-shaped manner. 

 Indeed, the aspect resembles thick and graceful tufts of grass with large spikes, for the granular 

 glands are mostly at the tips of the streaks of mucus, a state probably due to their passage 

 outwards under compression. Professor Keferstein figures this in Borlasia splendida, but he 

 does not refer thereto in his descriptions. In the fresh specimen the glandular papillae 

 are much smaller than in the Enopla, and widely different in shape (Plate XVII, fig. 20, 

 and Plate XVIII, fig. 14), the former representing them in the extruded proboscis, the latter as 

 viewed from without. Under ordinary circumstances they have an ovoid form, and vary from 

 T^oo"^ 1 to Wooth of an mcn m s i ze - Under pressure they become either flattened circular 

 bodies, or assume a cylindrical and slightly barred aspect ; and, after escape into the surrounding 

 water, the contents are club-shaped or rounded (Plate XVIII, fig. 12). 



