. Outlines of zoology. liac artery, and (i5) byportal veins from the intestine (the hepatic portal system); h\oo&leaves the liver by hepatic veins which enterthe hepatic sinus. Blood passes into the kidneys [a)from the renal arteries, and (b) byrenal portal veins from the caudal,pelvic, and lumbar regions (the renalportal system); blood leaves thekidneys by posterior cardinal veins,which enter the cardinal sinus. Into the precaval sinus there alsoopens the lymphatic trunk. The heart lies in a pericardialcavity, which is connected with theabdominal cavity by two fine canals,and is an anterior p
. Outlines of zoology. liac artery, and (i5) byportal veins from the intestine (the hepatic portal system); h\oo&leaves the liver by hepatic veins which enterthe hepatic sinus. Blood passes into the kidneys [a)from the renal arteries, and (b) byrenal portal veins from the caudal,pelvic, and lumbar regions (the renalportal system); blood leaves thekidneys by posterior cardinal veins,which enter the cardinal sinus. Into the precaval sinus there alsoopens the lymphatic trunk. The heart lies in a pericardialcavity, which is connected with theabdominal cavity by two fine canals,and is an anterior part of the blood contains, as usual, redblood corpuscles and leucocytes. The dark red spleen lies in thecurve of the stomach. The redthyroid gland lies just in front ofthe anterior end of the ventral thymus is represented by awhitish body dorsal to each of thefirst four gill-clefts. Each begins asa patch of endoderm, and this isinvaded by migratory mesenchymecells which multiply as Fig. 288.—Urogenital organsof male skate. T,^ Testis ; Ep.^ epididymis ; ^vas _ deferens ; K.^ kidney ; ^seminal vesicle; ^ sperm ,, urogenital sinus; CI., cloaca. Excretory and reproductive systems.—The dark red kid-neys lie far back on eachside of the vertebral column. They are developed from the hind part of the mesonephros. Several tubes from each kidney combine to form a ureter. The two ureters of the male open into the urogenital sinus, whence the waste products pass out by the cloaca; in the female they open into little bladders,—the dilated ends of the Wolffian ducts,—and thence by a common aperture into the cloaca. EXCRETOR Y AND REPRODUCTIVE S YSTEMS. S47 The segmental duct of each side divides into Wolffianand Miillerian ducts. The Wolffian duct becomes in themale the vas deferens, in the female it is an unimportantWolffian duct; the MuUerian duct becomes in the femalethe oviduct, in the male it is a mere rudiment. The muscles
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Keywords: ., bookcentury1900, bookdecade1910, bookidcu3192, booksubjectzoology
