80 ORGANIC DEPENDENCE AND DISEASE 



sents only the life of the species Onychaster flexilis, may 

 have been an attack upon the crinoid animal through its 

 oral aperture. But whether it intimates an actual state of 

 dependence or might under favorable circumstances have 

 developed into a true parasitism we do not have to decide, 

 as nature quickly wiped out the combination through causes 

 which we cannot know. 



THE WORK OF PSEUDOPAEASITIC BORING 

 ORGANISMS 



On almost every sea beach one can find the shells of dead 

 or living mollusks bored full of minute tubes. No skeleton 

 of the sea, except those essentially free of lime, escapes the 

 attack of the borers. And as our present beaches and sea 

 grounds abound with these things, so did the seas of the 

 Paleozoic ages. 



Such borings and borers have been much studied in their 

 living form, an interesting literature has grown up about 

 them, and perforations of like character in ancient fossils 

 have been occasionally noticed. There can be no denial of 

 their important present and past activity in the breaking- 

 down of accumulated lime and its return to the sea waters. 

 Kolliker 1 pointed out in much detail the general diffusion 

 of certain boring "vegetable parasites" among the many 

 varieties of calcareous shells in the existing fauna and he, 

 with others, the vast total of dissolution of lime wrought 

 by this agency alone. Such shell perforations have been 

 ascribed to different organisms, both animals and plants ; to 

 the algae and fungi, to the boring sponges and to the bor- 

 ing worms. The more conspicuous rock excavations made 

 by such boring mollusks as Teredo and Pholas 2 and nestling 



1 Annals and Magazine of Natural History, ser. 3, v. 4, p. 300. 1859; 

 Zeitschr. f. Wissensch. Zoologie, v. 10, p. 215, pi. 15, 16. 1860; Quar. Jour. 

 Microscop. Sci., v. 8, p. 171. 1860. 



2 Boring mollusks are known from Paleozoic seas and Whitfield has figured 

 such an occurrence (Corallidomus concentricus in the coral Labechia) from the 

 Ordovician of Ohio (see "Geology of Ohio," v. 7, p. 493, pi. 13. 1893). 



