MONOGBAPH OF THE EXISTING CRINOIDS. 125 



edge of the recent forms shoukl have been able to appeal i)ersonally trj masters 

 of the palaeontological side of the subject. 



The most striking feature of the history of the study of the structure and devel- 

 opment of the comatulids is that the work has been practicaUj- confined to species 

 of the genus Antedon, and has mostly been done on ^. mediterranea. Hamann, P. H. 

 Carpenter, Ludwag, Semper, Danielssen and Perrier include more or less discus- 

 sion of a few other forms, usually IleUometra glacialis or Cornanthus panicirra; a 

 little is to be found concerning Neocomatella alata, Tropiometra carinata and T. picta, 

 and Leptometra phalangium, and on tlie pentacrmoid young of Ilathrometra, with 

 short notices on the pentacrinoids of certain other species, especially of Leptometra 

 phalangium and IleUometra glacialis. But even a beginning has scarcely been made 

 in the study of the comparative anatomy of the comatulids, while we know nothing 

 whatever in regard to the comparative development, except in the case of three of the 

 sjiecics of Antedon, the observations on one of which were made as far back as 1863 

 and have never been reviewed. 



OUGAXIZATION' OP THE CUINOIDS. 



General remarks. 



Before taking up in detail the description of the various structures and organs 

 which collectively make up the crinoid whole, it is necessary to give a brief account 

 of what, in the opinion of the author, a crinoid is, and to indicate in sis few words 

 as possible the relationship between the crinoids and other organisms, both within 

 and without the phylum Echinodermata. 



Within a very few years it has been suggested by two investigatoi-s, working 

 quite independently, that the echinoderms are not by any means the highly anoma- 

 lous creatures that they have heretofore always been considered, but that they are 

 in reality a very aberrant offshoot from the acraniate crustacean stock, finding 

 their logical systematic position beyond the barnacles. 



The present author was led to this conclusion through a careful study of the 

 adult crinoidal nervous system which, though highly complicated and very anoma- 

 lous, is seen when analyzed to belong to the typo especiallj' characteristic of prim- 

 itive crustaceans, while Prof. William Patten arrived at the same result through 

 a critical comparative study of the development of the echinoderms and of the 

 primitive crustaceans, and a study of the abnormal young of the latter. 



Of the echinoderms as a whole. Prof. Patten writes: "The echinoderms are 

 notable for their contrasts and contradictions. Their outward appearance and 

 their pronounced radial structure distinguish them from jdJ other aniniixls, and at 

 first sight suggest a very primitive organization similar to that of the coelenterates. 

 On the other hand, they display a high degree of histologicjJ and anatomical special- 

 ization that is in marked contrast with their low grade of organic efficiency. They 

 begin their early embryonic development with a bilaterally symmetrical bodj- and 

 with clear indications of metamerism, only to change it in the later stages for one 

 that is radially symmetrical and in which all outward traces of metamerism have 

 disappeared. After a short free swimming larval existence they attach themselves, 



