. A manual of zoology. Zoology. ooO ARTlIROrODA mented liv a ventral chain composed oi ganglia mctamcrically arranged. The most e\ident dislinclions liet\\-ecn the annelids and the arthropods are (i) the character of the segmentation and {^) the presence of joiitted appendages. In superficial appearance the lines helween tJte segnienls are con- stricteil more deeply in lite arthropods than in the annelids. The cause of litis lies in the character of the inieguntent (tig. .vi, /'), wlticlt is developed as a Itard armor, in which two lavers are rccogitizahle, e]>iderntis (â h>podermis
. A manual of zoology. Zoology. ooO ARTlIROrODA mented liv a ventral chain composed oi ganglia mctamcrically arranged. The most e\ident dislinclions liet\\-ecn the annelids and the arthropods are (i) the character of the segmentation and {^) the presence of joiitted appendages. In superficial appearance the lines helween tJte segnienls are con- stricteil more deeply in lite arthropods than in the annelids. The cause of litis lies in the character of the inieguntent (tig. .vi, /'), wlticlt is developed as a Itard armor, in which two lavers are rccogitizahle, e]>iderntis (â h>podermis') and the cltilinous layer. Tlte epiilermis is a lltin epithelium, wliile the chitinous la}-er is of greater iliickness and, since it is secreted by ihe epidermis, is stralilied parallel to the surface. Its lirmness is due to c'lil'ni, wliich is unlike most organic sulislaitces in its resistance to acids and alkalis; only under the action of sulphuric acid and heat is it broken up into gram'of AriliTopoJ ^ugar and ammonia. Freciuently (Myriapods, Crus- jointing; .t, in ex- tacca) the cliitiuous armor is strengthened l>y the. panded, B. in traded comiilioii; 1-4, rings with con- necting membranes, tlie muscles inili- cated by dotted lines, (, a '' 11^ r G ruber). deposilioit of calcium carbonate and phosphate. A firm coat would render tlte animal incapable of motion were there not joints between tlte parts. \Mtile ihe segments themsel\es are heavily armored, the cuticle between them is redticed to a delicate articular skin, and this is so protected by a kimi of telescoping of the segments that injury in these softer regions is itearly impossible (lig. 304). Since the ringing of the body is connected witli this armoring, it disappears with the need for such protection. The hermit crabs (lig. 40O) illustrate this. These animals li^â e with the abdomen inserted in a snail shell. That part of the body which projects from the shell is armored, while the abdomen is soft- skinned
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectzoology, bookyear1912
