80 
ORGANIC DEPENDENCE AND DISEASE 
sents only tlie 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 PSEUDOPARASITIC 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. Wissenseh. 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). 
