EARLY ADAPTATION IN THE FEEDING HABITS OF THE 



STAR-FISHES. 



By John M. Clarke, Ph.D. 



On several previous occasions the author has had opportunity to bring out 

 rather interesting facts bearing on the very early history and primitive beginnings 

 of certain organic activities which may fairly be characterized as bad habits; 

 that is, "bad" from the point of view the observer naturally assumes as a member 

 of the human community which catches the full cumulative effect of these habits 

 as they have come down the ages with increased force and with roots sunk deep 

 into the constitution of human society. I have hoped and still feel there is 

 reason to hope that the close pursuit of these ancient evidences of adjustment 

 into habits that still prevail among living organisms may lead to a better under- 

 standing of dependent conditions of life as they present themselves to us today. 



The habits which I have been able to elucidate, or at least predicate for cer- 

 tain very ancient, wholly paleozoic creatures, are those of dependence resulting 

 from adaptation — evidences of mutualism some of which date back even to the 

 opening stages of the earliest Ordovician, with every indication of a previous exist- 

 ence in the Cambrian times. They are not alone conditions of symbiosis but early 

 indications of the positive degeneration which commensalism invariably implies. 

 Such arrangements were effected in the primitive faunas by the sessile worms 

 which selected their hosts with variant taste among the florescent colonies of 

 corals and sponges; wherever indeed there seemed to be a large and energetic 

 working surface which would be to their feeding advantage. These associations 

 are intimate and singular; and while these groups continue to associate in sym- 

 biotic condition to the present, in those most ancient days they assumed some 

 peculiar expressions no longer recognized. 



So with the barnacles and corals; with the corals upon themselves. The 

 little wormlike Myzostomum, all of whose living species are parasitic on the 

 crinoids, seems to have acquired this dependent habit back in these paleozoic 

 days. Habits of boring by the sponges and algae were so extremely common in 

 the ancient faunas of the earth that the dead shells lying on the bottom of the 

 old seas are found to be often punctured and riddled by the tubes of these little 

 creatures. 



Of rather momentous interest is the condition displayed by one case of 

 genuine paleozoic parasitism — that of the gastropods upon the crinoids— an 

 instance of abject dependence whose beginning we have reason to believe is well 

 understood and is indeed most significant. We know that in the Ordovician days 

 certain round-mouthed snails had acquired a loose association with the crinoids. 



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