PHORMOSOMA ZEALANDT/E. 107 



may throw any light on the subject. IJiit we cannot expect this to he 

 done at once. The demands of modern systematists must of necessity he 

 met gradually, and one's predecessors are not to be unhesitatingly con- 

 demned because they have not included in their work some more modern 

 point of view. 



The study of pedicellariae has only added a new factor dilfcring in no 

 way in its potentiality from those formerly in use. I may (]uote again 

 from Dr. Mortensen : ^ "When no pronounced difference is found between 

 large and small pedicellarioe, it may in fact be impossible to decide whether 

 a certain specimen is to be regarded as a large or a small form." Surely 

 this acknowledgment that the pedicellarioe cannot be classified may throw 

 some doubt, on the statement that " the pedicellaria3 give absolutely excellent 

 systematic characters." 



Dr. Mortensen recognizes only such affinities as are indicated by the 

 structure of the pedicellariae. Affinities indicated by other structural features 

 have little or no interest for him, or are entirely erroneous. It will be a 

 great saving hereafter if illustrations of Echini are limited, as he would have 

 us limit them, to figures of pedicellariae. 



Dr. Mortensen says,^ " even if the structure of the tests were identical, we 

 cannot be warranted in classing them together ; for, as has constantly been 

 shown by these examinations, identical structure of the test is no proof of 

 near relationship." We are perfectly justified in retorting that similarity of 

 the pedicellariae is no proof of relationship as shown by the structure of the 

 test, and we are not warranted in classifying together forms which agree 

 only in the structure of the pedicellariae, and differ in the structure of the 

 test. 



Dr. Mortensen^ does not fail to perceive that pedicellariae are not likely to 

 be of frequent use in the determination of fossil forms, and for that reason 

 condemns the classification of all fossil forms, and, in passing, of the Irregu- 

 lar Echinoids. It certainly would be most valuable to be able to determine 

 fossil Echinoids with all the data available for their modern representatives, 

 for the present we must be satisfied to acknowledge the limitations of 

 our work. Even among the living Echinoids we have not as yet a mono- 

 graphic description of the principal types of the Desmosticha and Petalo- 

 sticha, to which we may refer the many new species which have been 

 described from the collections of recent deep-sea explorations. There is still 



^ Mortensen, 1. c. p. 9. ^ Mortensen, 1. c. p. S5. * Mortensen, 1. c. p. S. 



