. Fig. 5. {a to u). Ceratias holbblli Kroyer. Allometric growth. Dimensions of Ceratias and Mancalias spp. plotted against standard length on a double logarithmic scale. (The numbers refer to individual specimens recorded in Table 1.) Ceratias holbolli is thus a blind fish in which the functional eyes of the young become reduced and then covered by opaque skin in the adult. There are certain other fishes which resemble C. holbolli in possessing eyes that are reduced and subcutaneous when adult, but functional in the juvenile stages. These are the Brotulids Lucijuga and Stygicola, and the goby
. Fig. 5. {a to u). Ceratias holbblli Kroyer. Allometric growth. Dimensions of Ceratias and Mancalias spp. plotted against standard length on a double logarithmic scale. (The numbers refer to individual specimens recorded in Table 1.) Ceratias holbolli is thus a blind fish in which the functional eyes of the young become reduced and then covered by opaque skin in the adult. There are certain other fishes which resemble C. holbolli in possessing eyes that are reduced and subcutaneous when adult, but functional in the juvenile stages. These are the Brotulids Lucijuga and Stygicola, and the goby Typhlogobius (Norman, 1931) The degree of negative allometry of the nostrils in Ceratias holbolli, although not so great as that of the eyes, is nevertheless pronounced. In the juveniles 'Mancalias tentaculatus' and ' M. bifilis', these organs are fairly conspicuous, and it is curious that they appear to have previously been overlooked. They are hollow tubercles projecting on each side of the head, half-way between the eyes and the edge of the premaxilla (Fig. 1B). In the adult Ceratias holbolli, as represented by Regan's and the Antarctic specimen, they become reduced, flattened and tag-like (Fig. iA). Although they still retain their lumen, it is probable that in this adult condition they are little or no better than useless vestiges. Even
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