104 ANATOMY OF THE ANOPLA. 



The usual cross of fibres occurs at one of the poles of the transverse section of the proboscis 

 of Linens marinus (Plate XXI, fig. 5), but the separate piece at the opposite pole is somewhat 

 larger than in L. gesserensis. The proboscis of Cerebratulus angulatus (Plate XXIII, fig. 18) 

 differs from the foregoing at one of the poles of the circle in transverse section. The layer of 

 circular fibres is divided into two bands, one of which (the inner) passes continuously round, 

 while the outer, after the usual intersection at one pole, diverges much more at the other, so as to 

 make a triangular space between its fasciculi. In the space thus formed is situated a band of 

 longitudinal fibres {ga). Further, in the outer angle of the cross, that is, in a position 

 agreeing with the wedge of fibres at the opposite pole, a narrow belt of longitudinal fibres exists 

 (gb). In the Lineus acuticeps of Dr. Baird, from St. Vincent's, West Indies (L. Guilding's 

 collection, British Museum), the cross made by the fibres is entirely absent, and this coincides 

 with a continuous and powerful longitudinal muscular layer within the circular coat. The 

 latter (inner longitudinal coat) also occurs in an example of the LineidcB collected by Dr. 

 Cunningham in Elizabeth Island. The Lineus novce-zealandice of Dr. Baird, again, agrees with 

 the ordinary British forms in regard to layers, but there is no cross of fibres at one pole. A small 

 form from Greenland also shows no intersection of the fibres, but the circular coat is divided 

 by a median line into two layers, and there is a complete inner longitudinal coat. In Borlasia 

 fflizaheth(B the white proboscis is extremely slender in proportion to the bulk of the animal, and, 

 moreover, the walls are comparatively thin. Instead of the shrinking and condensation which 

 usually occur on immersion of the organ in spirit, a considerable central cavity remains in 

 this case. Externally in transverse section (Plate XIX, fig. 7) is a thin investment, which 

 generally shows a central line, as if divided into two layers. Beneath is a coat of 

 longitudinal fibres, and then a thin belt of circular fibres with the ordinary glandular lining. 

 The papillae of the latter are small, rounded, and minutely granular. Meckelia asulcata is dis- 

 tinguished from other Lineidm by the structure of its proboscis (Plate XX, fig. 5), which has 

 externally no distinct superficial layer. Its outer coat consists of densely woven spiral fibres, 

 which at opposite poles in the sections cross each other more distinctly than at other parts. 

 The next (inner) coat consists of a considerable layer of longitudinal fibres, upon which the 

 glandular papillae rest. 



In Micrura the organ is furnished with somewhat slender papillae, which assume various 

 shapes under pressure. When viewed laterally, the rounded or flattened papillae, that formerly 

 seemed only granular, appear to be composed of a series of minute rods set closely together 

 (Plate XVIII, fig. 13). In some, however, the striae are longitudinal. When extruded from 

 the organ into the water, the cylindrical bodies in the papillae cling together in some instances 

 like fibrillae ; and the appearance in the prepared specimens is quite characteristic, the inner 

 surface being covered with a vast number of these elongated structures. The latter are the 

 bacillary bodies described by Dr. Max Midler, but I have never seen in the British species any 

 of the urticating organs mentioned by this author. The anatomy of the organ in this section 

 agrees with that in Lineus, and in spirit-preparations the shrinking causes a protrusion of tissue 

 at the separate segment opposite the intersection of the fibres. 



In Carinella annulata the proboscis has externally a thin investment composed of two layers 

 (Plate XX, fig. 6), the outer consisting of elastic and the inner of circular muscular fibres ; then a 

 thick layer of longitudinal fibres is met with, and, lastly, a coat of circular fibres, to which the glan- 

 dular lining is attached. Rod-like bodies occur in the papillae of the latter coat, as in other forms, and 



