. Fresh-water biology. Freshwater biology. AQUATIC EARTHWORMS 63s. Development of budding zones in Stylaria lacustris. A, An early stage. B, A later stage. C, Still later stage with a second budding zone well started. X2S. (After Leuckart.) gives rise to a definite number of new somites (five in most species of Naididae), which form the anterior part of the posterior daughter- worm. The daughter-worms, before separation, may in turn de- velop budding zones, and in some cases even a third series of these zones may appear and thus give rise to chains of incipient individuals, or zooids. In some
. Fresh-water biology. Freshwater biology. AQUATIC EARTHWORMS 63s. Development of budding zones in Stylaria lacustris. A, An early stage. B, A later stage. C, Still later stage with a second budding zone well started. X2S. (After Leuckart.) gives rise to a definite number of new somites (five in most species of Naididae), which form the anterior part of the posterior daughter- worm. The daughter-worms, before separation, may in turn de- velop budding zones, and in some cases even a third series of these zones may appear and thus give rise to chains of incipient individuals, or zooids. In some spe- cies chains of eight zooids are of ordinary occur- rence. In the genus Chaetogaster the plane of division is in a septum between two somites. Although many aquat- ic OHgochaeta have the power to regenerate missing parts, greatly developed, there is lack of evidence that it is of much importance in normal reproduction. Environmental Relations. The well-known investigations of Darwin and others, on the action of terrestrial earthworms on the soil and its organic contents, have led to a general appreciation of the importance of the relations of these animals to their surround- ings. It is less generally understood that their aquatic relatives play a very important part in reducing the great masses of aquatic vegetation to a finely-comminuted condition. OHgochaeta of various species abound in the mud at the bottom and along the shores of most bodies of fresh water, and an almost continuous stream of this mud with its deca3dng organic contents is passing through their bodies and being still further subdivided and de- prived of organic material and its available energy. Niunerous other species swarm in the decaying leaves and stems of coarse vegetation of swampy areas and materially aid in their disintegra- tion, while still other kinds populate the floating masses of algae, which they rapidly devour as decay progresses. Since under favorable conditions it requires but two or th
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectfreshwa, bookyear1918
