. Animal life as affected by the natural conditions of existence. Animal ecology. PAKASITBS ON COEALS. 335 itself round in a spiral. At the same time it appears so to stimvilale the base of the coral that it grows faster than the cup itself, and thus the base gradually but conspicuously outgrows the cup. Many corals are affected in a perfectly similar manner by parasitic crustaceans; Diaseris Freycineti by certain Cirrhi- pedia of which the shells often greatly outgrow the foot of the Diaseris, though this too is abnormally extended. Certaia species of the genus Heterocyathus also are infested
. Animal life as affected by the natural conditions of existence. Animal ecology. PAKASITBS ON COEALS. 335 itself round in a spiral. At the same time it appears so to stimvilale the base of the coral that it grows faster than the cup itself, and thus the base gradually but conspicuously outgrows the cup. Many corals are affected in a perfectly similar manner by parasitic crustaceans; Diaseris Freycineti by certain Cirrhi- pedia of which the shells often greatly outgrow the foot of the Diaseris, though this too is abnormally extended. Certaia species of the genus Heterocyathus also are infested by Sipun- culidse just like Heteropsammia, and their growth is modified by them. Even in fossil species of this genus holes are often observable in the foot which can scarcely have been anything else than the dwellings of Sipunculidse.''" There are also, it is true, some species of the same genus, Heterocyathus, which. Fig. 86.—BfiAeropsammia Michelird. a, seen from above with the broad base; 6, from below, with the tube of the Aspidosiphon partly opened ; c, also from below but intact, showing the large entrance of the tube and the small side openings. establish themselves on the shells of univalves; the animals which have formed these are invariably dead, and the cavity of the dead shell is always occupied by another of the Sipuncu- Udce; but in this last case the worm has had no effect on the growth of the coral, which has followed the normal course of its species aiid is at most so far modified that the coral, in order to obtain as secure a hold as possible, has extended its base rather more widely over the surface of the shell than seems to be its natural habit. In the genera Heteropsammia and Heterocyathus, in the second place, another generic character becomes modified in a very peculiar manner by the Sipunculidce. All the species attacked, of both genera, display both on the under side of the. Please note that these images are extracted from scanned page images
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Keywords: ., bookcentury1800, bookdecade1880, bookpublishernewyo, bookyear1881
