. Fresh-water biology. Freshwater biology. -â -7 Body much compressed, pellucid. Eye small, with numerous projecting lenses and little pigment; no ocellus. Spine ordinarily above middle of valves, directed upward. Crest very variable, often enormous. Claws with two pectens, the distal of 7-9 teeth. Anal spines 7-12. Sum- mer eggs ordinarily 2; sometimes as many as 6. Length, $, to mm., besides spine, which may reach mm. Widely distributed in limnetic region of lakes. Shape of head extremely variable; all forms from var. breviceps Birge, where the crest is hardly visible, to the extreme
. Fresh-water biology. Freshwater biology. -â -7 Body much compressed, pellucid. Eye small, with numerous projecting lenses and little pigment; no ocellus. Spine ordinarily above middle of valves, directed upward. Crest very variable, often enormous. Claws with two pectens, the distal of 7-9 teeth. Anal spines 7-12. Sum- mer eggs ordinarily 2; sometimes as many as 6. Length, $, to mm., besides spine, which may reach mm. Widely distributed in limnetic region of lakes. Shape of head extremely variable; all forms from var. breviceps Birge, where the crest is hardly visible, to the extreme of extension shown by retro- curva proper. This species replaces in the United States the European D. cucullata, which is related to D. longi- spina, much as this form is to O. ptUex. D. retrocurva never has the extremely acuminate form of head wbichcucullala sometimes shows. Very probably study will show that all the pulex forms (31, 32, 33) must be imited into one polymorphic species. 34 (26) Claws without pecten 35 35 (38) Ocellus present, though small. Daphnia longispina (O. F. Miiller) 1785 . 36 Spine long; claws without pecten. Male without long papilla on posterior part of body. This species is so variable that almost no characters can be given for it. It is less robust than the pulex forms, ordinarily fairly transparent; often hyaline. Thispart of the species divides at once into 2 sections or subspecies, each with numerous varieties which have never been thoroughly studied in the United t).5 MM. Fig. 1068. Daphnia 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 Ward, Henry Baldwin, 1865-1945; Whipple, George Chandler, 1866-1924. joint author. New York, John Wiley & sons, inc. ; [etc. ,etc. ]
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectfreshwa, bookyear1918
