. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. FEEDING IN MELLITA 83 function appears to be entirely that of locomotion. Similar spines are found all around the margin of the test hut they are almost twice as thick (1300/A X 160/A) ; they are densely arranged anteriorly and more scattered posteriorly. Their extra thickness is probably correlated with stresses set up during movement through the sand in a horizontal direction. Non-ambulatory or protective spines of the oral surface are shorter and thinner (430/AX 30/A) than ambulatory ones and are often bent near the middl
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. FEEDING IN MELLITA 83 function appears to be entirely that of locomotion. Similar spines are found all around the margin of the test hut they are almost twice as thick (1300/A X 160/A) ; they are densely arranged anteriorly and more scattered posteriorly. Their extra thickness is probably correlated with stresses set up during movement through the sand in a horizontal direction. Non-ambulatory or protective spines of the oral surface are shorter and thinner (430/AX 30/A) than ambulatory ones and are often bent near the middle of their length (Fig. 3, B) ; they cover all the re- maining areas of the oral surface. Similar spines are found in the lunule and on the aboral margin of the lunule they form a protective ring projecting up higher than the other spines of the aboral surface; here they prevent very large sand particles from entering the lunule and blocking it. On the aboral surface there are two types of spine distributed together all over the animal. The larger of these are club-shaped spines which move the. A/ FIGURE 3. The principal types of spine found in Mcllita sexiesj>erforata. A = Ambulatory spine with abraded tip. B = protective spine of oral surface. C : - Two views of club-shaped spines of aboral surface. D = Aboral miliary spine. sand grains posteriorly over the aboral surface (Fig. 3, C). The club-shaped head of these spines is set at a slight angle to the stem and its tip is oriented toward the margin of the test. The others or miliary spines (Fig. 3, D) are shorter than the club-shaped spines and are characterized by having a sac-like swelling on the tip; this sac contains yellowish granules which stain darkly with toluidine blue. The epithelium at the base of the cilia on these spines stains purple with the same stain and it seems plausible therefore to suggest that these spines are the principal site of mucus secretion. Miliary spines also occur on the inner walls of the l
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
