FOURTH REPORT OF THE DIRECTOR IQO/ 



if'5 



sion. In the present seas all gastropods of truly parasitic habit 

 are parasites on the Echinoderma, the class to which the crinoids 

 belong. Crinoids are few today and appear to be relatively free 

 from these attachments, but their allies, the starfish and sea 

 urchins, are still beset by the gastropods, often so reduced by the 

 degeneration of their condition as to be scarcely recognizable. 

 This far-reaching and general condition of depravity would seem a 

 direct inheritance of the ancient conditions we have portrayed.^ 



Crinoids and Starfish 



We have some very interesting instances of association be- 

 tween the crinoids and the ophiuran Onychaster flex- 

 i 1 i s Meek & Worthen. Three of these are here figured, one a 

 copy from Wachsmuth and Springer's figure ofActinocrinus 

 multiramosus W. & Sp., the others drawn from specimens 

 in the possession of Mr Fred Braun. In the first the starfish has 

 encircled with its arms the dome of the crinoid, mouth downward 

 in such an attitude as to suggest though probably not to demonstrate 

 that it was diligently attending to the waste of the crinoid. As the 

 arms of the crinoid have been broken awa}^ the" act of the starfish 

 is exposed in all its nakedness. In the specimens of the Onychaster 

 with Barycrinus hoveyi Hall, the arms of the two creatures 

 have become completely entangled and fixation for feeding purposes 

 at least is entirely effective. In respect to the end sought and 

 attained this condition is one of parasitism but one still subject to 

 the control of the individual. There seems no reason to assume 

 that the starfish is here endeavoring - to suck the life out of the 

 crinoid itself and it would be going further than the facts justify to 

 interpret this demonstration solely as an act of feeding like that of 

 the common starfish of today in its attacks upon the oyster. 



I quote here some remarks from Wachsmuth and Springer's 

 North American Crinoidea Camerata [1897, p. 566], concerning the 

 relations of Platyceras and Onychaster to the high domed crinoid 

 Actinocrinus multiramosus. 



Of this large and beautiful species we obtained at Indian Creek 

 and Canton over forty specimens, most of them in excellent pre- 

 servation, with the arms attached; and it is very remarkable that 

 nearly one half of them have either a Platyceras attached to the 



'The brothers Sarasin have described a very interesting case of the parasitic attachment 

 of a limpetlike Platyceras to a living starfish, in which the former by an extension of its 

 mouth into a snout which penetrates the test of the starfish, sucks out the nutritious fluids 

 Ergebniss einer Forschurigsretse nuf Ceylon, v. /J, While the parasitic condition between 

 che limpets and crinoids of the Paleozic was elastic, this is fi.xed and beyond repair. Other 

 living snails parasitic on the allies of the crinoids are interestingly described in the Natur- 

 ivissenschaftliiha Wochenschrift, January 17, 1904. 



