BASAL PLATES IN CRINOIDEA CAMERATA 495 



radials did not affect the basals of di cyclic crinoids" in the same 

 manner as in the monocyclic. While in the latter, when the plate 

 is represented, the orientation of the basals is slightly disturbed, 

 in the dicyclic forms it remains unaltered. The anal plate of the 

 latter rests invariably upon the trunkated upper face of the pos- 

 terior basal; while in monocyclic crinoids it is supported by the 

 basals a and e (Nos. 10 and 12), or occasionally by a and x (No. 8). 

 This statement leads one to believe that no widening of the 

 posterior basal took place upon the introduction of the anal plate 

 in the dicyclic form, but Nos. 15-18 in Fig. 1 show a decided widen- 

 ing of that plate. Overlooking this inconsistency and the fact that 

 trunkation of the posterior basal is in itself an alteration, we are 

 still unenlightened as to why alteration is demanded in the one 

 case and not in the other, as no explanation of an alternative 

 phenomenon is given. Neither is any reason given, other than the 

 position of sutures, for the markedly different positions of enlarge- 

 ment in basal plates of the four-, three-, and two-basal hexagonal 

 forms. By reading between the lines one is able to supply various 

 explanations, yet they are not the explanations of the writers, nor 

 what is needed and demanded by the conditions of the problem. 

 Furthermore, no reasons nor illustrations are given showing why 

 the abnormal specimen of Teleiocrinus umbrosus, by which the 

 theory was apparently confirmed, was oriented with the smaller 

 basal in the left anterior interray. The questions in the writer's 

 mind are: Why should the stimulus of enlarging the anal area in 

 the quadripartite form cause enlargement of the right side of the 

 posterior basal and not of the left or of both sides as well ? Why 

 should the same stimulus in a dicyclic crinoid have no effect upon 

 the adjacent basal plates ? Why should the same stimulus cause 

 the enlargement of the left anterior basal in the equibasaled, tri- 

 partite form, and of the left side of the right anterior basal in the 

 equibasaled, bipartite form, derived therefrom? What was the 

 nature of the change in shifting factor x from basal c to basal d? 

 How could such changes take place without disturbing the orien- 

 tation of any plate, compound or simple ? What were the reasons 

 for the orientation assigned to the abnormal specimen of Teleio- 

 crinus umbrosus ? These questions have led the writer to investigate 



