. The microscope and its revelations. whilst those of the lateral arelarge and serrated. The palateof Trochus zizyphinus, repre-sented in fig. 707, is one of the most beautiful examples of thisform, not only the large teethof the lateral bands, but thedelicate leaf-like teeth of thecentral portion having theiredges minutely serrated. A yetmore complex type, however, isfound in the palate of which there is a central bandof teeth having nearly straightedges instead of points ; then, oneach side, a lateral band consisting of large teeth shaped like thoseof the shark ; and beyond this,
. The microscope and its revelations. whilst those of the lateral arelarge and serrated. The palateof Trochus zizyphinus, repre-sented in fig. 707, is one of the most beautiful examples of thisform, not only the large teethof the lateral bands, but thedelicate leaf-like teeth of thecentral portion having theiredges minutely serrated. A yetmore complex type, however, isfound in the palate of which there is a central bandof teeth having nearly straightedges instead of points ; then, oneach side, a lateral band consisting of large teeth shaped like thoseof the shark ; and beyond this, again, another lateral band on eitherside, composed of several rows of smaller teeth. Very curiousdifferences also present themselves among the different species ofthe same genus. Thus in Doris pilosa the central band is almostentirely wanting, and each lateral band is formed of a single rowof very large hooked teeth, set obliquely like those of the lateralband in fig. 707 ; whilst in. Doris tuberculata the central band is the 3 o 2. w- FIG. 707.—Palate of TrocliiiK zi,~i/pliinus. 932 MOLLUSCA AND BEACHIOPODA part most developed, and contains a number of rows of conical teeth,standing almost perpendicularly, like those of a harrow (fig. 708). Many other varieties might be described did space permit; butwe must be content with adding that the form and arrangement ofthe teeth of these palates afford characters of great value in classi-fication, as was first pointed out by Professor Loven (of Stockholm)in 1847, and has been since very strongly urged by Dr. J. E. Gray,who considers that the structure of these organs is one of the bestguides to the natural affinities of the species, genera, and families ofthis group, since any important alteration in the form or position ofthe teeth must be accompanied by some corresponding peculiarity inthe habits and food of the Hence a systematic examinationand delineation of the structure and arrangement of these organs, bythe aid of
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectmicrosc, bookyear1901
