By M. W. Hardisty
The proliferation of clinical texts and their swiftly escalating expenditures calls for of an writer a few justification for the construction of another specialized quantity; really one who treats of a comparatively imprecise workforce of animal- the Cyclostomes-whose importance is little liked outdoor the circle biologists. but, in the zoological literature this workforce of vertebrates has regularly commanded a level of recognition, particularly dispropor tionate to the relatively small numbers of species concerned or their fiscal significance. This distinct curiosity stems more often than not from their exact phylogenetic prestige. Asjawless vertebrates the hagfish and the lamprey are considered as the only survivors of a as soon as flourishing workforce of Palaeozoic vertebrates-the Agnathans-amongst that are numbered the 1st verte brates to seem within the fossil checklist. due to this courting to the fossil agnathans it used to be inevitable that previous dialogue of the phylogenetic signifi cance of the cyclostomes must have been ruled via comparative anatomists and palaeontologists, even supposing lately their certain evolutionary place has more and more attracted the curiosity of comparative physiologists and scholars of molecular evolution. in the final fifteen years either the hagfish and the lamprey were the topic of separate courses describing intimately many facets in their morphology, body structure and existence cycles (Brodal, A. and Fiinge, R., The Biology ofMyxine, 1963; Hardisty, M. W. and Potter, I. C., The Biology of Lampreys, 1971-72.
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