. Animal activities : a first book in zoölogy. Zoology; Animal behavior. I04 ANIMAL Notice the form of one of the swimmerets on the second or third abdominal segments and compare all the swimmerets with this. How do the other swimmerets differ from the ones first exam- ined ? Infer a use for the sixth pair of swimmerets. Sketch a swimmeret, naming parts. Compare the ends of the legs having pincers with those which do not have those organs. How much extra growth would be needed to produce a pair of pincers on the last pair of legs ? Examine all the jointed ap- pendages on one side
. Animal activities : a first book in zoölogy. Zoology; Animal behavior. I04 ANIMAL Notice the form of one of the swimmerets on the second or third abdominal segments and compare all the swimmerets with this. How do the other swimmerets differ from the ones first exam- ined ? Infer a use for the sixth pair of swimmerets. Sketch a swimmeret, naming parts. Compare the ends of the legs having pincers with those which do not have those organs. How much extra growth would be needed to produce a pair of pincers on the last pair of legs ? Examine all the jointed ap- pendages on one side of the How many do you find ? Counting a pair of appendages to each segment or somite, how many segments has a crayfish or shrimp ? How do the mouth-parts of a crayfish or shrimp differ from those of a grasshopper } Remove one side of the carapace and expose the gill-cavity. Do you find gills at the base of all the legs } Do you see the spoon-shaped gill-scoop .^ Of what appendage is it a part ? Look on the inside of the basal joints of the legs to find the outlets of the reproductive organs. Among crayfish the females have these openings on the middle pair of legs and the males on the last pair. With the help of the drawings find the openings of the green glands (renal openings). Find the ear. Where is the anal opening ? Internal Structure. With an alcoholic specimen one can make out the parts indicated in the figure below. The position of the heart, digestive tube, and Fig. 90. — Fourtli Ab- dominal Segment of Crayfish. /, tergum; st, sternum; //. pleu- rum; /r, protopodite; €71, endopodite; ex, ex- opodite. One append- age has been removed. 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 French, Nathaniel S. (Nathaniel Stowers), 1854-. New York ; London : Longmans, Green, and Co.
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Keywords: ., bookcentury1900, bookdecade1900, booksubjecta, booksubjectzoology
