Gamier ate Monocyclic Grinoids. 207 



processes of growth that could even permit it. Had Mr. Wilson not 

 been in communication with Mr. Springer, I should have said that 

 he had taken Wachsrnuth & Springer's diagrams more seriously than 

 those authors ever intended, and that his criticism was more laboured 

 than the case demanded. At any rate he has swept the field clear, 

 and his own conclusions may be discussed on their merits. They 

 are : — 



"1. The ancestor of the monocyclic Camerata was a simple, 

 generalized crinoid with pentamerous symmetry." 

 If "generalized" means "Inadunate", then this supports the 

 suggestion that I have more than once opposed to the views first of 

 Wachsmuth & Springer and later of Professor Jaekel. 



" 2. The base of the pentagonal Camerata is not the result of 

 reversion from an intermediate hexagonal stage, but is in a primi- 

 tive condition as far as influence of the anal plate is concerned." 

 The sting in this seemingly obvious statement is the corollary that 

 the quadripartite base of the Melocrinidae (Fig- 2) cannot be derived 

 from that of such a form as Xenocrinus (Fig. 5). Such a derivation 

 is one of the views above alluded to as inconsistent with my taxonomy. 

 I have therefore no qualms in accepting Mr. "Wilson's conclusion. 



"3. The anal plate is of secondary origin, and originated by 

 primary interpolation between the latero-distal margins of the 

 posterior radials." 

 It is cheering to note Mr. "Wilson's dismissal of the view that the 

 anal x is a supplementary plate, suddenly introduced, and his clear 

 exposition of its origin from some plate lying above the radials, 

 which plate gradually grew downwards at its lower margin and 

 became resorbed at its upper margin, without any disturbance of 

 adjacent plates (see Geol. Mag. 1899, pp. 40 & 44), and I welcome 

 the extension of this theory to the Camerata. 



"4. The hexagonal base of the monocyclic Camerata [our 



Figs. 5, 6 & 9] resulted from the separation of the posterior 



radials and trunkation of the posterior basal by the anal plate, the 



anal plate having been interpolated by portion al migration in the 



space created by the demand of the hind-gut for enlargement." 



This is a consequence of conclusion ]S"o. 3, and is a restatement of 



Beyrich's sentence (1871, p. 51): "Da das Hexagon nur dadurch 



entsteht, dass zwei Radien durch ein Interradialfeld bis zur Basis 



herab auseinandergeschoben werden. . . ." 



" 5. The widening of the posterior basal upon interpolation of 

 the anal plate was bilaterally symmetrical." 



This is not merely a statement of result, comparable to the 

 conclusion of Beyrich's sentence: "so erhalt das Hexagon fur des 

 Krinoid die Bedeutung eines symmetrischen Hexagons, u.s.w.," but 

 it means that the posterior basal expanded equally on either side of 

 the axis of symmetry, and not merely on its right side. In 1898 

 I pointed out that, as a statement of result even, this did not apply 

 to all crinoids, but probably Mr. Wilson intends to refer only to 

 Monocyclic Camerata. In them it can apply only to the hexagonal 



