. Outlines of zoology. Zoology. 334 ARACHNOIDEA AND PALAZ0S7RACA. ostia. Hsemocyanin is present as usual as the respiratory pigment of the blood, and there are oval corpuscles. From an anterior aorta, like that of the scorpion, two vessels are given off which bend backward, unite with lateral arteries from each chamber of the heart, and form a collateral vessel on each side of the heart. These unite in a posterior dorsal artery. From the anterior aorta two other branches unite in a ring around the nerve-collar, which gives off vessels to the limbs, and is continued backwards around the nerve-c
. Outlines of zoology. Zoology. 334 ARACHNOIDEA AND PALAZ0S7RACA. ostia. Hsemocyanin is present as usual as the respiratory pigment of the blood, and there are oval corpuscles. From an anterior aorta, like that of the scorpion, two vessels are given off which bend backward, unite with lateral arteries from each chamber of the heart, and form a collateral vessel on each side of the heart. These unite in a posterior dorsal artery. From the anterior aorta two other branches unite in a ring around the nerve-collar, which gives off vessels to the limbs, and is continued backwards around the nerve-cord. From capillaries the blood is gathered into a ventral venous sinus, whence it passes to the respiratory organs, and thence to the pericardium and heart. The respiratory organs or gill-books are borne by the last five appendages. Each looks like a much-plaited gill, or like a book with over a hundred hollow leaves. The leaf-like folds are externally washed by the water, and within them the blood flows. The leaves of the gill-books are compared to the leaves of the lung-books of scorpions. If this homology is correct, the gill-books are evaginations, the lung-books in- vaginations, of the skin. The reproductive system.— The males are smaller than the females. The testes are very diffuse, the two vasa deferentia open on the internal surface of the operculum, and the spermatozoa, which are vibratile, are shed into the water. The ovaiies form two much-branched but con- nected sacs; the oviducts are separ- ate, and enlarge before they open beneath the operculum. Spawning occurs in the spring and summer months. The ova and sper- matozoa are deposited in hollows near high-water mark. Some of the early stages of development, still impei- ectly known, present considerable resemblance to corresponding stages in the scorpion. In the larvte, both cephalothorax and abdomen show signs of segmentation, but this disappears. The spine is represented only by a very short plate, and the lar
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Keywords: ., bookauthorth, bookcentury1800, bookdecade1890, booksubjectzoology
