. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. NATURAL HISTORY OF SHIPWORM. 275 ments not only indicate some growth but also that a considerable variation exists in the relative measurements. The range of variation in ratio of length to breadth and also in length of hinge line is great. Veligers fed upon diatoms for one week meas- ured from .077 x .090 mm. to .081 x .093 mm. The size at- ( ^ I B ft A R Via tained at the time of metamorphosis was not learned, but Nelson ('23) gives it as .25 mm. in length. I have collected several hundred young metamorphosing Teredo, whic
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. NATURAL HISTORY OF SHIPWORM. 275 ments not only indicate some growth but also that a considerable variation exists in the relative measurements. The range of variation in ratio of length to breadth and also in length of hinge line is great. Veligers fed upon diatoms for one week meas- ured from .077 x .090 mm. to .081 x .093 mm. The size at- ( ^ I B ft A R Via tained at the time of metamorphosis was not learned, but Nelson ('23) gives it as .25 mm. in length. I have collected several hundred young metamorphosing Teredo, which had burrowed into wood, varying in age from two to three weeks after settling. These range in size from .35 mm. to I mm. The smaller ones in two weeks have almost completed metamorphosis and have from two to three rasping ridges or rings of growth on the shell. Individuals three weeks old have four rings of growth and a typical Teredo shell. At three weeks of age the Teredo is prac- tically spherical and its burrow, when exposed by cutting away the surface of the wood, is a hemispherical pit. The young worm now begins to elongate rapidly and at the end of one month its burrow measures from 5 to 7 mm. in length, and has a diam- eter of 2 to mm. The shipworm when expanded fills its bur- row so that, in measuring the rate of growth, the size of the burow may be taken as the correct measure of the enclosed worm. When the shipworm is removed from its burrow, it contracts to one half or two thirds of its expanded measure. Tables 5 and 6 show the rate of growth from the egg to adult size, and need not be described in detail. Measurements were taken every three or four days, and the rate of increase in size from day .to day was found to be surprisingly rapid. It should be noted that the ages given in the tables include only the time that elapsed from the time of settling. If the age from the egg is desired, about thirty-five days should be added to these figures to include the ti
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
