The evolution theory . B. Fig. 107. Larva of a Caddis-fly, after Rosel. A, removed from its case,showing the hooks Qi) which attach it thereto, and the whitish abdomen,covered only by a thin cuticle. B, the same larva, moving about with its case. perhaps hardly to the same degree, for while these larvae maketheir own houses, and will therefore at least make them big enoughto begin with, the pressure and friction must increase with thegrowth of the animal. If the regulation of the strength of the integumentary skeletonbe referred to selection, we see at once why carapace and wing-coversshould b
The evolution theory . B. Fig. 107. Larva of a Caddis-fly, after Rosel. A, removed from its case,showing the hooks Qi) which attach it thereto, and the whitish abdomen,covered only by a thin cuticle. B, the same larva, moving about with its case. perhaps hardly to the same degree, for while these larvae maketheir own houses, and will therefore at least make them big enoughto begin with, the pressure and friction must increase with thegrowth of the animal. If the regulation of the strength of the integumentary skeletonbe referred to selection, we see at once why carapace and wing-coversshould be of equal thickness throughout their whole extent, and whythey do not disappear, although they do not function actively, andare less stimulated than any other parts of the skeleton; and wealso understand why the abdomen of hermit-crabs and of larvalPhryganidse and Psychidae has become soft, whether it be exposedto pressure or friction in a greater or a less degree. It no longerrequires to be hard, because it is protected
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Keywords: ., bookauthorthomsonj, bookcentury1900, bookdecade1900, bookyear1904
