Chap. III. GENUS BOLINA. 259 



The anastomosis with the large lobe is established through a tube which arises 

 from the lower sinuosities of the inner convolutions of the long ambulacral tuljc. 

 The communication with the oral tube is more direct, and may be considered as 

 a branch from the tul)e of the short ambulacra : indeed, both may be considered 

 so, the anastomosis with the large lobe, as well as that with the mouth. But, in 

 the first case, the communication with the tube of the long ambulacra is more 

 indirect ; while the connection with the oral system is direct, through a tube which 

 only bends at right angles upon itself 



The large lol^es and the auricles are not identical in their structure, though 

 homologous with one another. Each large lobe is formed of the actinal prolon- 

 gation of two imited spheromeres, while each of the small lobes or auricles is an 

 actinal prolongation of a distinct spheromere. Moreover, the large lobes are bulky 

 and thick, consisting of a large mass of the same kind of large cells of Avhich the 

 whole body is built ; while the small lobes are simply membraneous, or rather 

 diverticula arising from a fokUng of the surface of the body at the lower extremity 

 of the short ambulacra, in the shape of flat sacs with hollow margins. They are, 

 indeed, a mere fold in the direct prolongation of the short ambulacra, along the 

 margin of which the ambulacral tubes and the locomotive flappers are continued 

 all round the lobe ; when the fringes disappear and the tube alone is continued, 

 branching into the adjoining large lobe, as well as towards the margin of the mouth. 

 We may therefore view the small lobes simply as modifications of the lateral 

 ambulacra, rising above the general surface of the body and bent inward in pro- 

 portion as the great transverse chasm which separates the two large lolies rises 

 hio-her along the sides of the mouth, thus leading to the formation of a loop in 

 the lateral ambulacra, instead of a straight course, as on the sides. The vibrating 

 frino-es of the small lobes are in direct continuation of the locomotive ,combs of 

 the ambulacra proper, which would appear as long on this side of the body, and 

 even longer, than upon the anterior and posterior spheromeres, if they were 

 stretched in the same manner ; but, Ijeing here folded over in the shape of promi- 

 nent aui'icles, they act more energetically as lateral oars. There is, however, one 

 marked difference between the ambulacral rows of locomotive fringes and their 

 continuation along the margin of the auricles. As far as the locomotive flappers 

 follow a straight course along the vertical ambulacra, their combs are transverse 

 to the chymiferous tubes ; but as soon as the tubes diverge sideways to follow 

 the margin of the auricles, the locomotive flappers assume a longitudinal arrange- 



rau.x " (the ambulacral tubes of the large lobes) nection between tlie ambulacral tubes of Pleuro- 



witli the '• vaisseaux jierigastriques inferieurs " (the brachia and its cueliac tubes (p. 0.37), which re.ally 

 coeliac tubes). What I did not observe was a con- does not exist. 



