38 Reviews — Wachsmutli 8f Springer^ s Monograph on Crinoids. 



detailecl discussion the hypothesis proposed by me in April, 1890/ 

 and already criticized by them in Pebrnary, 1891.- Long ago^ 

 I showed that their representation of my views was based on 

 misconceptions, and again,* while accepting a part of their criticism, 

 took the opportunity of re-stating my main position. By ignoring 

 these protests in this Monograph, Messrs. Wachsmuth and Springer 

 have readily gained credit for the apparent demolition of my 

 supposed theories. A short re-statement of views already published 

 by me may therefore be pardoned. 



First, then, I have maintained "that the lowest, median, posterior 

 plate of the ventral tube is always this same plate {x), whether 

 it be right above the radials, as in locrinus and Merocrinus, resting 

 on the radials, as in Heterocrinus and Castocrinus, between the 

 radials but not in line with them, as in Homocrhms and Dendrocrinus, 

 in line with the radials, as in Botryocrintis and Cyathocrinus, or rising 

 above the radials again, as in the later Decadocrinidas [_Delocriniis, 

 Ulocriniis, Erisocrinus^ and in the larval Anledon." ^ Any objections 

 to this homology based on an alleged difference between anals and 

 tube-plates, or on the supposed impossibility of plates sinking into 

 the cup, have already been proved groundless by the admissions and 

 arguments of the objectors themselves. Moreover, since, as regards 

 the other anal plates (EA, ri), it is now admitted that change took 

 place by gradual modification of constant elements, the burden of 

 proof should lie with those who imagine the sudden introduction 

 of a new element. The statement of Messrs. Wachsmuth and 

 Springer that " this question was not discussed by Bather," however 

 true it may be for my paper of 1890, is hardly one that should have 

 been published five years after I had discussed the question in more 

 than one place. As for the 1890 paper, it must be remembered that 

 the distinction between tube-plates and anals was not attempted by 

 Wachsmuth and Springer till 1891.* 



Secondly, I showed that if the known genera were arranged in 

 a series according to the admitted evolution of the radianal, then 

 one could trace a gradual descent of the proximal median plate of 

 the anal tube, from the left shoulder of the right posterior super- 

 radial, to a position between the posterior radials and resting on 

 the posterior basal ; and, following this, the descent of rt from a yet 



1 Ann. Mag. Nat. Hist. (6), vol. v, pp. 319-334. 



2 Proc. Acad. Nat. Sci. Philadelphia, yoI. for 1890, pp. 345-392. 



3 Ann. Mag. Nat. Hist. (6), vol. vii, pp. 480-489, June, 1891. 



* Ann. Mag. Nat. Hist. (6), vol. ix, pp. 64-66, Jan. 1892. 



* Loc. cit. ult. 



* In reply to their present assertion (p. 128) that they had always regarded the' 

 proximal posterior plate of locrinus and Merocrinus " as a plate of the tube," and 

 had " never made any statement from ■which he might infer that we thought it 

 represented the plate x ; yet he quotes us in his diagrams as if we had done so in 

 1879," it is enough to say that in plate xvi of their "Eevision of Palseocrinoidea," 

 1879, the letters an are aj^plied equally to the median line of tube-plates in locrinus, 

 to the plate which they now and always have homologized with the proximal of those 

 median plates in Anomahcrinus and Hybocrinus, and to the plate x of Cyathocrinus. 

 "With tliis before me, why on earth should I have introduced into a diagram doubts 

 that had never occurred to me or anyone else ? 



