UINTACRINUS; ITS STRUCTURE AN^D RELATIONS. 35 



positions. The cases of imperfect development in size or number of infra- 

 basals (PI. IL, Figs. 4 to 9) may correspond to stages of transition from 

 one form to the other. 



We have, therefore, in pursuing this matter farther, to choose be- 

 tween these alternatives : (I) That from the eggs of either a monocyclic 

 or dicyclic Crinoid both forms were indiscriminately hatched ; or (2) that 

 they hatched in one form, with a tendency in the larva to develop into the 

 other, which tendency irregularly became effective in some individuals, 

 and ineffective in others ; or (3) that after the larval stage, by some process 

 of addition, subtraction, or consolidation among the hard parts of the 

 test, a dicyclic Crinoid was transformed into a monocyclic, or vice versa. 

 Whichever of these be accepted to account for the observed facts in 

 Uintacrinus^ we have no reason to say that the same thing may not have 

 occurred in other Crinoids, from the earliest Paleeozoic times. And if 

 so, the transition from the one form of base to the other would seem 

 to be not so difficult or impossible as has been assumed. Nor does 

 it seem that this character can be taken wnth such absolute certainty 

 as the leading one upon which — above all others — the phylogenetic 

 classification of the Crinoids must be based, and to which all other char- 

 acters must yield. If within a single species, dicyclic and monocyclic 

 Crinoids can by some of these processes be indiscriminately produced, 

 where is the difficulty in conceiving that both monocyclic and dicyclic 

 genera might have arisen in some similar way, and flourished side by side 

 within the limits of a primitive family like the Reteocrinidae ? If one 

 can be derived from the other ontogenetically, why not phylogenetically, 

 within orders, sub-orders, and families ? 



The relative importance of characters as evidence of descent is, 

 and must remain — at least when dealing with extinct forms — largely 

 a matter of individual opinion. It has often been said that every scheme 

 of classification is only an expression of the opinion of the author at the 

 time of its promulgation, and I do not see that this statement loses much 

 of its force with the progress of investigation. Whether, in the arrange- 

 ment of the Crinoids, Dicyclica and Monocyclica shall be held to be sub- 

 divisions of the great groups of Camerata, Inadunata, and Flexibilia, or 

 of lesser divisions, or whether these shall be considered as subdivisions of 

 the Monocyclica and Dicylica, cannot, in my judgment, be settled with 

 our present knowledge. Which way the thread of consanguinity was 



