210 



Prof. F. J. Bell on the Arrangement and 



Ecbinoderms fixed by their aboral pole. It is among the 

 Caliculata only that the question of pelmatozoism arises. 



But it is the next to be faced, for, although the Holo- 

 thurians exhibit clear signs of affinity with the primitive 

 Echinoderm derived from a generalized worm, the " Cystids " 

 show no less definitely that they are extremely archaic forms. 

 It is stated by Barrande that Lichenoides had no stalk, and 

 there is a general agreement among students of the group 

 that there were some of the so-called Cystids that were never 

 fixed and had not fixed ancestors. In other words, there 

 were apelmatozoic and pelmatozoic Cystids. 



Pelmatozoic 



Apehnatozoic 



Anactinogonidial 



Actinogonidial. 



Holothurians. 



Cystidea. 

 Cystidea. 

 Cystidea. 



Non-Caliculate. Caliculate. 



The relations of the forms are shown objectively in the 

 accompanying table. The rearrangement of the Cystidea 

 has long been recognized as a serious want. 



The apelmatozoic actinogonidial Cystids divide into two 

 main branches : one leads to the strictly pelmatozoic forms, 

 that is forms that were fixed or had ancestors that were fixed ; 

 the other leads to the Echinoidea, Asteroidea, and Opliiu- 

 roidea ; the former may be called the Statozoa, the latter the 

 Eleutherozoa. 



Of the relations -inter se of the pelmatozoic series I propose 

 to say nothing more ^ ; but there remain a few generalizations 

 to be made regarding the rest, or the Echinozoa in the sense 

 of some authors. When, however, we have said that they 

 are apelmatozoic and actinogonidial (which is also true of 

 some of the other series), we have said about all that is true 

 of them, save that they are eleutherozoic. When we come 

 to see in what they differ we cannot find sufficient justifica- 

 tion for their union under the common name Echinozoa, as a 

 mark distinguishing them from all other Echinoderras. 



* I suppose no morpbologist will be bold enough to say whether 

 Mars%ipites or the irregular Blastoids are primarily or secondarily free 

 forms. 



