W. C. M'INTOSH ON VALENCINIA ARMANDI. 75 



present on each side. A thin ring of circular muscular fibres can now be traced all 

 round the united area of the proboscis and the vascular canals, the great transverse 

 bands being inflected at each side where the circular fibres pass. Between the united 

 area and tbe circumference of the body we have now the ever- increasing ganglia, which 

 rest inferiorly on the outer division of the inferior transverse band, and are bounded 

 superiorly by the outer fibres of the upper transverse band. Externally they apparently 

 abut on the basis-layer. About this region a curious maculation of the part within the 

 basis-layer is observed, especially superiorly — a feature due to the presence of two or three 

 narrow longitudinal separate layers of muscular fibres, which form a complete investment. 

 Just in front of the mouth they form a rather thick compound layer, best marked supe- 

 riorly and inferiorly ; but the advent of the oral aperture separates the latter into two 

 great masses. Some circular fibres also appear to be present at the basis-layer, but they 

 are much less conspicuous than the longitudinal. A section made through the ganglia, 

 almost in the plane of both commissures (fig. 3), shows three rows of these interrupted 

 muscles (d') superiorly and inferiorly ; but the lateral regions are less distinct. The 

 ganglia (h) surround the united area of the proboscidian and vascular systems ; and, besides, 

 their other investments have increased in complexity. The external circular and internal 

 longitudinal fibres of the area still form a complete ring ; but there is also an inferior 

 appendix in the shape of a canal (s) on each side, separated from the great vascular tunnel 

 by a powerful transverse band (m). From the centre of the latter superiorly springs a 

 process ( p), which separates the great vascular tubes, and terminates above in the circular 

 coat of the proboscidian chamber (a o). Then, shortly afterwards, a series of longitudinal 

 fibres appear in the isthmus between the vascular channels, and run round the inner 

 circular coat, which further presents on its inner surface a complete lining of longitu- 

 dinal fibres. The two vascular canals appended to the inferior border of the transverse 

 band are soon separated by a broad transverse belt, and by-and-by are obliterated by the 

 mouth. The broad transverse belt just mentioned spreads out on each side underneath 

 the diminishing ganglia ; and some of the inferior fibres join the external longitudinal 

 series of separate muscles. The only representative of the great longitudinal muscular 

 layer afterwards so highly developed is a narrow arch (fig. 4, d), extending from the upper 

 end of each great vascular channel, and meeting at the raphe in the dorsal median line. 

 This, however, soon increases in thickness, and presents two channels (fig. 4, vs) between 

 its inner surface and the proboscidian sheath ; while behind the mouth it quite encircles 

 the body. The circular muscular coat (c) likewise completes the circuit of the body 

 immediately after the mouth. The separated layer of longitudinal fibres (d') outside 

 the circular layer soon breaks up into small fasciculi, which, in transverse section, form 

 a dotted belt outside the nerve-cords. 



There is thus a very characteristic difference between this form and Valencinia linei- 

 formis or Carinella. In V. lineiformis the snout, though very much longer in front of 

 the mouth, is less complex, there is only one vascular channel (of large size) on each 

 side of the proboscidian canal, and the ganglia have no longitudinal fibres between them 

 and the basis-layer. Erom without inwards there are the cutis, basis-layer, and circular 

 muscular fibres, while the rest of the area, with the exception of the three channels just 



SECOND SERIES. — ZOOLOGY, VOL. I. M 



