. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. ani cl. Fig. 10. Claspers of various holocepholian forms. A, Squalorajo; B, Chimaera monstrosa; C, Rhinochimoero atlantica. ant. c)., Anterior clasper; bos., basal; cl., clasper; , pelvic girdle; ppb., prepubic processes; r., fin-rays; , vertebral column. (After Leigfi-Sharpe.) Leigh-Sharpe interprets this cavity as ho- mologous to that of Chlamijdosdachc and so brackets these fishes together. Surely a common category for these forms stands on shaky ground. The Holocephali should probably be set apart even h
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. ani cl. Fig. 10. Claspers of various holocepholian forms. A, Squalorajo; B, Chimaera monstrosa; C, Rhinochimoero atlantica. ant. c)., Anterior clasper; bos., basal; cl., clasper; , pelvic girdle; ppb., prepubic processes; r., fin-rays; , vertebral column. (After Leigfi-Sharpe.) Leigh-Sharpe interprets this cavity as ho- mologous to that of Chlamijdosdachc and so brackets these fishes together. Surely a common category for these forms stands on shaky ground. The Holocephali should probably be set apart even here if the pres- ence of their curious frontal and anterior claspers is taken into consideration. Although the kidneys have not been thoroughly examined histologically, their gross anatomy and their relationship to the genital organs have been well described (Burlend, 1910; Leydig, 1851). There is no doubt that these organs, too, are like those of elasmobranchs and quite different from those of other fishes. Unlike the kidneys of the cartilaginous forms, those of bony fishes never become closely involved with reproductive structures in the male and, in both sexes, are generally unifonTi in tubule- structure throughout their length, under- going neither transformation nor degenera- tion at the anterior end as the animal reaches maturity. It is not necessary to lean entirely upon structural resemblances to predicate a possible relationship between the Holocephali and the Selachii either. The excretory systems of both groups bear the same distinctive functional earmark: the kidneys resorb urea selectively and maintain that substance in the bloodstream in unusually high concentration. In adult holocephalians, as in sharks, urine is produced in the posterior regions of the kidney and drained by specially de- veloped ureters. This arrangement contrasts with that of bony fish in which urine is produced throughout the entire kidney and is removed through the opisthonephric duct. In car
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