87 



water-vessel and the radial nerve. In the Brisinga on the contrary, the perivisceral 

 cavity extends, as in the Asteridae, through the whole length of the arms between the 

 ambulacral skeleton and the dorsal skin, containing in its basal part various internal 

 organs. 



10) Radial continuations of the digestive system (radial cseca) are never found in the 

 Ophiuridae; while in the Brisinga they are developed precisely in the same manner 

 as in the Asteridae. 



11) No special masticatory apparatus (teeth, dental papillae) are to be found in the Bri- 

 singa any more than in other Asteridae. But on the other hand the furrow-spines 

 situated on the interior contiguous adambulacral plates assume a particular develop- 

 ment, just as in other star-fishes, forming the so-called oral spines. 



12) The organ of secretion noticed in the Brisinga. with its issue on the dorsal side of the 

 disc, is something which we find only in the proper star-fishes. 



13) The so-called ,,heart", to which nothing corresponding has yet been noticed in the 

 Ophiuraus, agrees, in its structure and in its relation to the other parts, entirely with 

 the same organ in the Asteridae, as is the case also with the situation and structure 

 of the stone canal. 



14) As the organs of generation in the Brisinga are confined to the arms only, we do not 

 of course find the genital fissures on the lower side of the disc which characterise the 

 Ophiuridae. 



15) The terminal organs of sense in the Brisinga find their most complete homologon in 

 the Asteridaj; while nothing corresponding is found in the Ophiuridae. 



16) The manner in which the Brisinga moves, is the same as in the Asteridae; that is to 

 say, essentially by the play of the water- feet only; and not as in the Ophiuridae by 

 the flexion of the arms. 



Considering all these important characteristics, the points of agreement with the 

 Ophiuridae which the Brisinga exhibits, namely the little rounded disc plainly distinguished 

 from the long thin arms, and the absence of cuticular pores and cuticular tentacles (respira- 

 tory tubes), must go for nothing. 



In order still better to understand the great conformity of the genus Brisinga with- 

 the proper star-fishes, we will once again briefly consider some of the most important 

 organs in the Brisinga, and institute a detailed comparison with the same in other star-fishes. 

 We will dwell chiefly on the solid calcareous parts which support the body and determine 

 its form. 



a. Homology of the ambulacral skeleton. 



(Tab. V). 



We have previously divided the ambulacral skeleton of the Brisinga into 2 parts : 

 the skeleton of the disc, and the skeleton of the arms; and this is so far correct, as the 



