| Comments |
P.61 left column bottom paragraph: "Chitinous structures are mainly of ectodermal origin in multicellular animals and form the characteristic exoskeleton of most of the invertebrates (ref 2), in contrast to collagenous structures, which almost entirely are of mesodermal origin. Chitin exceptionally constitutes more than half of the total organic matter in chitinous structures. Higher concentrations of up to 85% are found in Arthropoda, which are particularly able to synthesize chitin. The shells of Gastropoda and Lamellibranchia, however, contain only small amounts of chitin." |