. Essentials of biology presented in problems. Biology. THE CRAYFISH 225 delicate. Oxygen, dissolved iu the water, pass(!s into the blood by os- mosis, during wliich process the blood loses some carbon dioxide. The gills are kept from drying \)y being plact^d in a nearly chjsed chamber, which is further adapted to its function by means of the row of tiny hairs which border the lower edge of the carapace. Thus crayfish may live for long periods away from water. Circulation. — The circulation of blood in the crayfish takes place in a system of thin-walled, flabby \essels which are open in places
. Essentials of biology presented in problems. Biology. THE CRAYFISH 225 delicate. Oxygen, dissolved iu the water, pass(!s into the blood by os- mosis, during wliich process the blood loses some carbon dioxide. The gills are kept from drying \)y being plact^d in a nearly chjsed chamber, which is further adapted to its function by means of the row of tiny hairs which border the lower edge of the carapace. Thus crayfish may live for long periods away from water. Circulation. — The circulation of blood in the crayfish takes place in a system of thin-walled, flabby \essels which are open in places, allowing the blood to come in direct contact with the tissues to which it flows. The heart Ues on the dorsal side of the body, inclosed in a delicate bag, into which all the blood in the body eventuaUy finds its way during its Crayfish with the left half of the body structures remoN'cd : a, intestines; b, \'cntral artery; c, brain; e, heart; et, gastric teeth; i, oviduct; I, digestive gland; m, muscles; ra, green gland (kidney); o, ovary ;Jji, pyloric stomach; r, nerve cords; d, cardiac stomach; st, mouth; u, telson; w, openings of veins into the peri- cardial sinus. Natural size. (Davison, Zoology.) Digestion. — Food which is not ground up into pieces small enough for the purpose of digestion is still further masticated by means of three teeth, strong projections, one placed on the mid-line and two on the side walls of the stomach. The exoskeleton of the crayfish extends down into the stomach, thus forming the gastric mill just described. The stomach is divided into anterior and posterior parts separated from each other by a constriction. The posterior part is lined with tiny projections from the wall which make it act as a strainer for the food passing through. Thus the larger particles of food are kept in the anterior end of the stomach. Opening into the posterior end of the stomach are two large digestive glands which further prepare the food for absorpt
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbiology, bookyear1911
