210 



Prof. F. J. Bell on the Arrangement and 



Ecliinoderms fixed by their aboral pole. It is among the 

 Caliculata only that the question of pelmatozoism arises. 



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

 thuriims exhibit clear signs of affinity with the primitive 

 Echinoderm derived from a generalized worm, tlie " Oystids" 

 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 



Apelmatozoic 

 Anactinogonidial. 



Actinogonidial. 



Holothurians. 



Cystidea. 

 Cystidea. 

 Cvstidea. 



Non-Oaliculate. 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 Ophiu- 

 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 ^qw 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 tliat is true 

 of them, save that they arc clcuthcrozoic. When we come 

 to see in what they dift'er we cannot tind sutficient justitica- 

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

 mark distinsiuishina- them from all other Ecliinoderms. 



* I suppose no morphologist will be bold enough to say Tvliether 

 Marsiipift's or the irrepulnr Hlftistoids are primarily or secondarily free 

 forms. 



