Sinopsis
This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1902. Excerpt: ... CHAPTER XXV THE CEPHALOCORDA--AMPHIOXUS LANCEOLATUS In the first volume of this work the frog, a vertebrated animal, was selected as an example of animal organisation, and in studying it the beginner will have gained a tolerably clear idea of the leading features of vertebrate structure. But the frog is by no means a simple vertebrate: almost every detail of its anatomy exhibits a complexity which forbids our regarding it as a near representative of that primitive stock from which, on the theory of evolution, we must suppose all vertebrate animals to have sprung. Happily for the study of comparative anatomy, we have an excellent example of a primitive vertebrate in the remarkable fish-like animal Amphioxus, found somewhat rarely on sandy bottoms in shallow waters off the English coast, but more abundantly in other parts of Europe, especially in the Mediterranean. Nor is Amphioxus confined to European waters; it has been found in shallow seas in almost every part of the world, and several species have been described, some exhibiting such well-marked characteristics that they have been thought worthy of generic rank. The common European species is named Amphioxus lanceoZatus, and it is the only one that will be referred to in the present chapter. Although Amphioxus is fish-like in form, it has neither the structure nor the habits of a true fish. It has neither head nor jaws, is destitute of paired fins, and has many anatomical peculiarities that are not found in any fish. It can swim rapidly in the water by sinuous movements of its narrow, knife-shaped body, but in its most usual posture it is buried vertically in the sand, the anterior end of its body projecting into the water. In this position it obtains its nourishment from the minute organisms drawn int...
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Reseña del editor
This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1902. Excerpt: ... CHAPTER XXV THE CEPHALOCORDA--AMPHIOXUS LANCEOLATUS In the first volume of this work the frog, a vertebrated animal, was selected as an example of animal organisation, and in studying it the beginner will have gained a tolerably clear idea of the leading features of vertebrate structure. But the frog is by no means a simple vertebrate: almost every detail of its anatomy exhibits a complexity which forbids our regarding it as a near representative of that primitive stock from which, on the theory of evolution, we must suppose all vertebrate animals to have sprung. Happily for the study of comparative anatomy, we have an excellent example of a primitive vertebrate in the remarkable fish-like animal Amphioxus, found somewhat rarely on sandy bottoms in shallow waters off the English coast, but more abundantly in other parts of Europe, especially in the Mediterranean. Nor is Amphioxus confined to European waters; it has been found in shallow seas in almost every part of the world, and several species have been described, some exhibiting such well-marked characteristics that they have been thought worthy of generic rank. The common European species is named Amphioxus lanceoZatus, and it is the only one that will be referred to in the present chapter. Although Amphioxus is fish-like in form, it has neither the structure nor the habits of a true fish. It has neither head nor jaws, is destitute of paired fins, and has many anatomical peculiarities that are not found in any fish. It can swim rapidly in the water by sinuous movements of its narrow, knife-shaped body, but in its most usual posture it is buried vertically in the sand, the anterior end of its body projecting into the water. In this position it obtains its nourishment from the minute organisms drawn int...
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