. Zoological Society bulletin . tains a hold, never loses it. Insome cases the rostrum is provided with re-trorsely curved hooks which catch in the mem-brane, or the cells of the lining wall of thethemselves. The corals and the millepores are» intestines are drawn into the suckers on themade fast by means of acalcareous secretion andthese also remain perma-nently fixed. Nearly all ofthe jellyfishes are free-swimming at all times, butthe primitive Leucernariahas the ability to attachitself at will by means ofan adhesive disc. The lar-val stage of Aurelia andcertain other jellyfishes issessile a
. Zoological Society bulletin . tains a hold, never loses it. Insome cases the rostrum is provided with re-trorsely curved hooks which catch in the mem-brane, or the cells of the lining wall of thethemselves. The corals and the millepores are» intestines are drawn into the suckers on themade fast by means of acalcareous secretion andthese also remain perma-nently fixed. Nearly all ofthe jellyfishes are free-swimming at all times, butthe primitive Leucernariahas the ability to attachitself at will by means ofan adhesive disc. The lar-val stage of Aurelia andcertain other jellyfishes issessile as a polyp for a pe-riod, in which condition itis known as a probably thoseof the common jellyfishAurelia flavidula, have livedfor some years in the bal-anced salt-water aquaria atthe New York propagate freely bysexual budding, but havenever metamorphosed intothe adult sexual condition. Rotifers.—The tiny wheel-animalcules arc cither freeliving, fixed or are two distinct meth-. WLrK t* j&m SEA-ANEMONES, WHITE CORALS AND HYDROIDSOtic half natural size. 976 ZOOLOGICAL SOCIETY BULLETIN. head of the worm. The fluke worms are pro-vided with one or more suckers by which theyretain their position upon or within the bodyof the host. Some of these worms apparentlydo not change their position once they have lo-cated themselves, but others move about moreor less. Many marine worms live permanentlyin tubes of calcareous or other matter, cementedto shells, rocks, etc. Leeches also anchor themselves when feedingby means of suckers, but these parasites affixthemselves only temporarily. The highly modi-fled myzostcmas, parasitic on crinoids and star-fishes, retain their hold by hooks on the appen-dages. Some of these external parasites moveabout over the host, while others live in a sessilecondition and stimulate the tissues of the hostto the formation of a sort of cyst somewhat likea plant gall. One species is an intestinal para-site. Bryozo
Size: 1540px × 1622px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, booksubjectzoology, bookyear1901
