'"i80'i^''] rRO('EP:DiN(ii=; of tfie national MusEr^r. 139 



of moderate .stieii.utli, hut towards the base two reiiioiis aio to be t'ouiul 

 upon the outer sui'lace of the teiitacde wliere the niusele i)i()ee8ses reach 

 an excessive (h'veh^piueut (IM. xix, V\^^. 7.) In sections which pass 

 throujih the [)oint of origin of the tentacles, just wliere they arise 

 from the disc (Tl. XX, Fig-. 10), it can be seen that these two nuiscle 

 bundles {tti) are continued ui)on the disc, forming' strong muscles lying 

 immediately over the mesenteries, one l)undle of each tentacle coming 

 from the mesoghea over each of the mesenteries which limit the in- 

 tramesenterial space to wliieh the tentacle belongs. These muscle bun- 

 dles are not, however, continued to any extent upon the disc towards 

 the mouth opening, but api)ear to be con lined to the i)eriplieral region 

 where the tentacles arise. 



The stomatoda'uni (PI. xix, Fig. St) is rather short, and has only one 

 siphonoglyphe which is deep, its mesoghea being nnich thicker than it 

 is elsewhere on the stonuitodeum. The renniinder of that structure is 

 nnxrked by six longitudinal ridges, eaeh of which corresponds to the 

 insertion of a mesentery. 



As is indicated by the furrows of the exterior of the column there 

 are twenty mesenteries. Eight of them are perfect, gonophorie, and 

 provided with mesenterial tilanieuts, while the remaining twelve are ini- 

 l)erfect, sterile, and destitute of tilaments. The arrangement of the 

 mesenteries is exceedingly interesting (Fl. xix, Fig. S). There are two 

 pairs of directives, having the characteristic arrangement of the longi- 

 tudinal nuiscles; that pair (FIT) which is attached to thesiphonogly]»he 

 marks the snlcar surface of the body. On each side of the sulcar 

 directives is an imperfect mesentery (V) with its longitudinal muscle 

 upon its sulcular surface, and succeeding this comes a perfect nu'sen- 

 tery (I) forming with the imperfect one a pair. Then follow a pair of 

 imperfect mesenteries (VIII), then a pair formed by a sulcar imperfect 

 (VI) and a sulcular perfect mesentery(IT), tlien a pairof iini)erfect mes. 

 eateries (VII), and tinally the sulcular din'ctives. 



It must be stated that the tigure I have given is to a certain extent 

 diagrannnatic, inasnnu'h as in a section through the stomatodauim the 

 longitudinal nuiscles of the imperfect mesenteries couhl not be rea<lily 

 made out, while further np the column, in sections which passed through 

 the column and disc, they were well develojied. 1 have reiiresented 

 therefore the arrangement as regards the perfectness or imperfectness 

 of the mesenteries as seen in a section i)assing through the stoma 

 todivum, but the musculature as seen in sections passing through the 

 column and disc. 



The h)ngitudinal muscles are not strong, and in the perfect mesen 

 teries occupy the greater part of the surface (IM. xx. Fig. 0). The 

 endoderm of the mesenteries presents a rathei' peculiar vacuolated ap- 

 pearam-e, remindingoneof the structure which it presents in (\-yi((iitlu(s. 

 The mesenterial lilaments which are developed only on the eight per- 

 fect mesenteries appear to lack the " Flimmerstreifen " but 1 can nut be 



