Febkuabt 24, 1911] 



SCIENCE 



295 



forded such factors had they ever existed, 

 leaves us a reasonable propriety to construe 

 the cessation of this parasitism as actually 

 accomplished in Carboniferous times, 

 and the recurrence of like associations 

 among allied animals of the present an 

 essentially new adaptation of the two. 

 For nature has made these adaptations 

 easily and degeneracy to the parasitic con- 

 dition is one of the facile procedures of 

 life, moving on apace with ever-increasing 

 momentum toward race destruction. Much 

 more natural, much more logical, much 

 better justified by well-known procedure in 

 these easy adaptations, is such a proposi- 

 tion, than that after millions of ages of 

 suppression the ancient abject depend- 

 ence of the limpet on the crinoid should 

 have reappeared as a direct inheritance 

 out of the remote past. It is to this point 

 I would direct the major purport of this 

 paper, for aside from all other questions of 

 ancient parasitic conditions there is none 

 yet of so profound biologic significance as 

 this question raised by the parasitism of 

 the Paleozoic gastropods on the crinoids. 

 Did the snails get over it? Did they con- 

 quer this habit of dependence and return 

 to normal independence? Granted that 

 the parasitic condition is but an expression 

 of adaptation; yet it unfailingly involves 

 degeneration. Did the gastropod rebound 

 from its degenerate adaptation and return 

 toward the normal living which has helped 

 to perpetuate its stock abundantly to the 

 present in more self-reliant expression? 

 I believe that all the positive and all 

 the negative evidence we can now ad- 

 duce on this deeply important subject 

 favors the presumption that the habit was 

 abandoned or at least, to speak in terms of 

 simple casuistry, was lost. We may give 

 the counter proposition all the weight to 

 which it is entitled, and I believe we ask 

 too much of both evidence and presumption 



to seek in it a recrudescence of a trans- 

 mitted acquired habit in the present after 

 the lapse of untold millions of years 

 between its appearances. 



Living nature can of its very essence 

 present us with no such proposition as this. 

 Here the time element is of paramount 

 importance and we are confronted then 

 here by the single example in all known 

 nature below man of the possible recovery 

 of a normal upright tendency in organic 

 living after a period of degeneration, of a 

 case of what appears to be, deducting due 

 allowance for possible uncovered records 

 among profoundly studied geological 

 faunas, an actual rebound from an adapta- 

 tion to evil living back to the normal up- 

 rightness of independent life by the inter- 

 vention of natural forces only. I might 

 cite to you additional interesting cases of 

 the parasitic habit in Paleozoic organisms, 

 but none which can now amplify the special 

 point I have had in mind in bringing these 

 succinctly to your notice. For doubtless if 

 nature could and did turn even an inverte- 

 brate sinner from the error of its ways 

 once, she can do it again ; she doubtless has 

 done it more than once and her influences 

 directed toward the demolition of such de- 

 generating adaptations could not be re- 

 stricted solely to lowly forms of life. The 

 supreme merit of the striking illustration 

 I have been able to bring to your attention 

 lies in the panorama of its history, its in- 

 ception, its progress, climax and probable 

 extinction. Even though it may now stand 

 alone, the argument from it could not be 

 much altered nor greatly strengthened by 

 supplementary eases, however it might 

 be clarified by the verification of the 

 negative evidence in the ages between the 

 Paleozoic and the present. But so far is 

 the evidence good and the logic sound 

 that I need not hesitate to intimate 

 that the parallelism between organic 



