Anatomy of the Temnopleurida\ 125 



podoiis. Tlie tentacles are moderately long and stout in 

 alcoholic specimens, and their bases are broad and encircle 

 the not very strongly marked peripodia ; the stem soon 

 becomes cylindrical and very slightly tapering, and it di- 

 minishes somewhat suddenly in diameter close to the large 

 suctorial or cup end. The hollow of the tentacle is well seen, 

 and it is the outcome of the junction of two short canals 

 which come through the two pores of each pair. The sepa- 

 ration between these canals is very slight in the base of the 

 tentacle. 



The plan adopted was to decalcify some specimens and to 

 colour and mount in balsam, and to mount others without 

 decalcifying them. 



In the decalcified specimens the tumid edges of the sucker 

 end are more or less faintly lobed, and there is evidently 

 some circular arrangement of fibres there. This would tighten 

 the grasp of the cup-shaped end, and would act upon the 

 quadripartite calcareous circlets wliicli will be mentioned 

 further on. A thick epithelium and much connective tissue 

 below it form the bulk of the cup, and are continuous with 

 the similar structures of the outside of the body of the ten- 

 tacle. On the body this structure is very delicate, and the 

 epithelium is rather more columnar tlian flat, it contains 

 granules and has cilia. In some tentacles there is much 

 thickening of the epithelial part near the neck of the cup, and 

 much transverse folding of it and the subjacent structures, 

 but elsewhere the cells may be excessively thin and trans- 

 parent. 



Four sets of muscular fibres are visible in a tentacle : 

 first, the circular fibres of the cup ; secondly, the concentric 

 and radiating fibres of the top of the tentacular cavity and 

 base of the cup (see Loven, ' Pourtalesia,' p. 49, pi. xi. 

 figs. 112-115) ; thirdly, the outer layers of circular fibres ; and 

 fourthly, the innermost muscular layer composed of longi- 

 tudinal fibres. The circular fibres are most developed near 

 the cup and in what may be called the neck of the tentacle ; 

 but elsewhere their presence varies most remarkably. In 

 some tentacles a delicate close layer can be distinguished 

 composed of exceedingly narrow, close, circular fibrils of 

 great slenderness ; they appear to be nucleated here and there 

 and separate 5 striation does not occur. In other examples 

 the circular fibres are very scarce and wide apart j in some 

 they do not exist. 



The longitudinal fibres reach from the base at the peripo- 

 dium, where they are stout and very visible, up the shaft, 

 where they become excessively attenuate and slightly dis- 



