. The microscope and its revelations. ilicious than calcareous ; and the variety of forms pre-sented by the silicious spicules is much greater than that whichwe find in the comparatively small division in which they arecomposed of carbonate of lime. The long needle-like spicules. whichare extremely abundant in several sponges, lying close togetherin bundles, are sometimes straight, sometimes slightly curved ;they are sometimes pointed at both ends, sometimes at one only;one or both ends may be furnished with a head like that of a 1 See Chapter V. of ilv. Saville Kents Man mil nfthf Iitfi<nt
. The microscope and its revelations. ilicious than calcareous ; and the variety of forms pre-sented by the silicious spicules is much greater than that whichwe find in the comparatively small division in which they arecomposed of carbonate of lime. The long needle-like spicules. whichare extremely abundant in several sponges, lying close togetherin bundles, are sometimes straight, sometimes slightly curved ;they are sometimes pointed at both ends, sometimes at one only;one or both ends may be furnished with a head like that of a 1 See Chapter V. of ilv. Saville Kents Man mil nfthf Iitfi<nt»-iu, and Chapter V. ofvol. i. of Mr. Balfours Comparative Embryology, as well as Professor Haeckels im-portant work on the Calcareous Sponuc--. 858 SPONGES AND ZOOPHYTES pin or may carry three or more diverging points which sometimescurve back so as to form hooks. When the spicules project from thehorny framework they are usually somewhat conical in form, andtheir surface is often beset with little spines arranged at regular inter-. B
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectmicrosc, bookyear1901
