. Animal biology. Zoology; Biology. 190 METAZOAN PHYLA thin shells and develop parthenogenetically. The winter eggs have thick shells, and development follows fertilization. The winter eggs require a considerable degree of acidity of the water to soften the shells so that they may hatch, and if this does not occur they are capable of living for many years and of still developing when placed under suitable conditions. A marked peculiarity of certain rotifers is their power to undergo drying and when again under favorable con- ditions to resume life activities. This ability and their small size
. Animal biology. Zoology; Biology. 190 METAZOAN PHYLA thin shells and develop parthenogenetically. The winter eggs have thick shells, and development follows fertilization. The winter eggs require a considerable degree of acidity of the water to soften the shells so that they may hatch, and if this does not occur they are capable of living for many years and of still developing when placed under suitable conditions. A marked peculiarity of certain rotifers is their power to undergo drying and when again under favorable con- ditions to resume life activities. This ability and their small size contribute to the ease with which they may be dispersed by the wind. This ease of dispersal by wind, added to the possibility of their being carried on the feet of water birds, has resulted in a distribu- tion which is of more cosmopolitan character than that exhibited by any other group of animals. 222. Phylum Bryozoa.—The animals included in the phylum Bryozoa (briozo'a; G., bryon, moss, and zoon, animal) are known -c^ ^, ..^ rr , in a general way as moss animals and sea mats. Fig. 101.—The rotifer Hyda- „, *= , • i i- wi • Hnasenta Ehrenberg. A, mature i hey are colouial lorms and their manner of female. B small degenerate male growth reminds ouc of the coloiiial hydroids, showing the large sperm sac but , c, but their structure distinguishes them very. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Wolcott, Robert Henry, 1868-1934; University of Nebraska (Lincoln campus). Dept. of Zoology. New York ; London : McGraw-Hill Book Company, Inc.
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