. Outlines of zoology. Zoology. CETACEA. 711 The heart is often cleft between the ventricles. Both arteries and veins tend to form retia mirabilia. The larynx is elongated, so that it meets the posterior nares, and forms a continuous canal, down which air passes from nostrils to lungs. The inspiration and expiration occur at longer intervals than in terrestrial mammals. The water-vapour expelled along with the air from the lungs condenses into a cloud, which is sometimes increased, by an accidental puff of spray. The kidneys are lobulated. The testes are abdominal. There are no seminal vesicle
. Outlines of zoology. Zoology. CETACEA. 711 The heart is often cleft between the ventricles. Both arteries and veins tend to form retia mirabilia. The larynx is elongated, so that it meets the posterior nares, and forms a continuous canal, down which air passes from nostrils to lungs. The inspiration and expiration occur at longer intervals than in terrestrial mammals. The water-vapour expelled along with the air from the lungs condenses into a cloud, which is sometimes increased, by an accidental puff of spray. The kidneys are lobulated. The testes are abdominal. There are no seminal vesicles. The uterus is bicornuate. The placenta is non-deci- duate and diffuse. The two mammae lie in depressions beside the genital aperture, and the milk is squeezed from special reservoirs into the mouth of the young. Usually a single young one is born at a time, and there are never more than two. All are carnivorous; but, while many feed on small pelagic animals, others swal- low cuttles and fish, and Orca attacks other Cetaceans and seals. Most are gregari- ous, and live in schools or herds. The living Cetaceans are ranked in two sub-orders—the Mystacoceti or Balsenoidea, without functional teeth, but with whalebone or baleen-plates on the palate, and the Odontoceti or Delphinoidea, with functional teeth and without baleen. Certain Eocene fossils, known as Zeuglodonts, are regarded by some (Lydekker, Dames) as primitive Cetaceans—Archaeoceti—less special- ised than modern forms, but Professor D'Arcy Thompson has advanced strong arguments in favour of their affinities with Pinniped Fig. 315.—Pelvis and hind-limb of Greenland whale (Baltena)—After Struthers. P., Pelvis ; F., femur; 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 Thomson, J. Arthur (John Arthur), 1861-1933. Edi
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Keywords: ., bookauthorth, bookcentury1800, bookdecade1890, booksubjectzoology
