The Vertebrate Skeleton

MONOTREMATA. In both genera the cranium is thin-walled, has a fairly large cavity, and is very smooth and rounded externally. The sutures between many of the bones early become...

=Hair=, which forms the characteristic Mammalian exoskeleton, varies much in different animals, and in different parts of the same animal. A large proportion of mammals have the...

The exoskeleton of the dog includes three sets of structures: 1. hairs, 2. claws, 3. teeth. =Hairs= and =claws= are epidermal exoskeletal structures, while =teeth= are partly of...

Some part of the integument at some period of life is always provided with hairs; these are epidermal structures arising from short papillae of the Malpighian layer of the epide...

In Invertebrates the hard, supporting structures of the body are mainly =exoskeletal=, in Vertebrates they are mainly =endoskeletal=; but the endoskeleton includes, especially i...

The species chosen for description is _C. palustris_, a form occurring throughout the Oriental region, but the description would apply almost equally well to any of the other sp...

The most primitive type of exoskeleton is that found in Elasmobranchs and formed of =placoid= scales; these are tooth-like structures consisting of dentine and bone capped with...

The exoskeleton of the Duck and indeed of all birds is entirely epidermal in origin. Its most important part consists of =feathers=, but it includes also the following horny str...

This great group includes the Reptiles and Birds and forms the second of the three into which the Gnathostomata may be divided. There is nearly always a strongly-developed epibl...

This generally has the form of overlapping horny =scales= which invest outgrowths of the dermis, and are found covering the whole body in most Rhynchocephalia, Ophidia, and Lace...

The most striking feature as regards the skeleton of the Turtle is that the trunk is enveloped in a bony box, the dorsal portion of which is called the =carapace=, while the ven...

(1) =Scales.= These are of the type known as =cycloid= and consist of flat rounded plates composed of concentrically arranged laminae of calcified matter, with the posterior mar...

The exoskeleton, at any rate in most living forms, is very slightly developed in Amphibia. The only representatives of the epidermal exoskeleton are (1) the minute horny beaks f...

The endoskeleton of the adult frog consists partly of cartilage, partly of bone and each of these types of tissue occurs in two forms. The cartilage may be hyaline, as in the om...

Three kinds of feathers are found, viz. (_a_) _pennae_ including quills and coverts, (_b_) down feathers or _plumulae_, and (_c_) _filoplumes_ which are rudimentary feathers. Th...

The notochord with its membranous sheath (1) may remain unmodified, or (2) may be replaced by bone or cartilage derived from the skeletogenous layer, or (3) may be calcified to...

The skin of the Newt is quite devoid of any exoskeletal structures. The only exoskeletal structures that the animal possesses are the teeth, and these are most conveniently desc...

The exoskeleton of the dogfish is mainly composed of placoid scales, each of which consists of a little bony base imbedded in the skin, bearing a small backwardly-directed spine...

THE following classification includes _only the forms mentioned in the succeeding pages_. The relative value of some of the terms employed in classification is not identical thr...

Birds form a large and extremely homogeneous class of the vertebrata, and are readily distinguished from all other animals by the possession of an epidermal exoskeleton having t...

THE animals included in this great group all possess an internal axial skeleton forming the vertebral column or back-bone; and a dorsal spinal cord. The vertebral column is deve...

AMPHIBIA differ markedly from Pisces in the fact that in the more abundant and familiar forms the skin is naked, and that when the integument is prolonged into median fins they...

(1) The =notochord=. This arises as a diverticulum from the alimentary canal which grows forwards into the proboscis and extends beyond the front end of the central nervous syst...