MONOGRAPH OF THE EXISTING CRINOIDS. 197 



discoverable in the interspace system of the central part of the calcareous reticu- 

 lation. 



There is among the crinoids, as in other animals, a pronounced lack of corre- 

 lation in the comparative development of the several organs and structures, mid 

 also in the cessation of development consequent on incipient senescence. The most 

 striking presentment of this is in regard to the skeletal system. In the early post- 



FlO. 127. UPPER MIDDLE PORTION OP THE COLUMN OF A SPECIMEN OP TELIOCRINVS SPRINGERI FROM THE WEST COAST OP 



INDIA, SHOWING THE CIRRI ARRANGED IN REGULAR WHORLS ON THE NODALS, wmca ARE SEPARATED BY A CONSTANT 



NUMBER OF INTERNODALS. 



larval stages this shows a very considerable advance over the other body elements ; 

 but it never attains a fixed maturity. All through the life of the animal it continues 

 to develop by accretion and by resorption, and the arms, except in rare cases, con- 

 tinue to add terminal segments until death occurs. After the adult stage is ivaclied. 

 however, change takes place very slowly, and at a constantly diminishing rate. It 

 is mainly evidenced by an increase in the size and in the solidarity of the compo- 

 nent elements, which gives old animals a peculiarly robust and rugged appearaiir, . 



