NEM ERTINEA— BAYLTS. 1 3 1 



einlxMlilcd aiiioiii;-, tin' fibres of the outer lougitudiiuil niuscle-laver (L.Ml). Tlie (li'ep 

 " primary hasement membrane," so conspicuous in L. (•nrfiujiifii^, separatino- the 

 ghuiilular layer from the muscuhiture, is entirely absent. 



The outer layer of longitudinal muscles (PI. II, tigs. 2, 3, 4, 5, L.Ml) is 

 exceedingly thick and well-developed. Its filjres are separated into groups only l)v 

 slight partitions of coimective tissue, so that under a low power of the microscope they 

 appear closely and evenly placed together, and the whole layer has a very solid aspect. 

 Between this layer and tlie circular muscles there is present the usual nerve-plexus 

 (PI. II, fig. 2, N.P.), witli tlio two large and well-developed lateral nerve-stems and a 

 small dorsal nerve. 



The circular muscle-layer (PI. II, figs. 2, 4, 5, t'.M.), like the outer Inngituibiial 

 layer, is very stout and solid in appearance. It is succeeded liy a comparatively tliin 

 inner longitudinal layer (L.M'.). The last two layers together make up a thickness 

 nearly ec^ual to that of the outer longitudinal (X)at. 



Ainuentdri/ ('(itud. — The intestine is U-shaped in transverse section (PI. II, fig. 2, 

 Int.), and without marked lateral diverticula. It seems to be characteristic of this 

 species that the " crypts," or pockets, in the lining epithelium — at least, in the 

 oesophageal portion of the gut — form very regular and acute angles. 



Piuib(isr/.s-s//iiif// anil Proboscif^. — The proboscis-sheath is larger in diameter, 

 relatively to tlie size of the whole animal, than tliat of L. rur/'in/dtus. Its lining 

 epithelium rests on (1) a thin I)asement-membrane, followed by (2) a thin longitudinal 

 coat of muscle-fil)res ; (3) a thin circular coat of muscles, connected dorsally with the 

 circular musculature of the l)ody-wall ; and (4) another coat of longitudinal muscles, 

 wliich is in reality part of the inner longitudinal coat of the liody-wall. 



The dorsal l)lood-vessel (PI. II, figs. 2, 4, 5, D.V.), or vessel of the rhynchocoele, 

 as it might more descriptively be called, lies, anteriorly, on the inside of the circular 

 muscles of the proboscis-sheath ; more posteriorly, it sinks through the circular 

 muscle-layer, and eventually comes to lie below it, among the outer longitudinal 

 muscles. It has very thick walls, as compared with the corresj)onding vessel in 

 L. ciin'/ii/iifiis. 



The proboscis is thin, and its musculature is not strongly developed. In trans- 

 verse section (PI. 11, fig. (>) some of the circular muscle-fibres are seen to cross each 

 other dorsally and ventrally (C, C), and pass outwards to the periphery, as in the 

 common ('in'elivatiihis inarijinafvx. Within the circular layer of muscles tliere is a 

 nervous laver, containing four large longitudinal nerves (N.). Tliere is no inner 

 longitudinal layer of muscles separating this nervous layer from tlie lining epitlielinm. 

 The latter is mainly composed of tall glandular cells. 



Vdsrnhir Si/sfciii. — The lilood-sinuses in the liead are arranged on a plan similar 

 in essential points to that of L. i;irrui]afu'<, already described; but after tlic I'-shaped 

 sinus has passed behind tlie (hu'sal commissure of the brain, its two arms extend 

 dorsally and outwards (PI. 11, fig. 4, B.S.), so as to embrace the dorsal ganglia and 



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