THE GROWTH OF CERATIAS HOLBOLLI 



17 



ID. BASE OF TENTACLE ON H EAO 

 TO BASE OF TENTACLE 

 [PAPILLA, PORE] ON BACK 



O. ANAL FIN TO CAUDAL FIN 



D. BASE OF TENTACLE [PAPILLA. PORE] 

 ON BACK TO DORSAL FIN 



P. BASE OF DORSAL FIN 



S. BASE OF ANAL FIN 



U. LENGTH OF NOSTRIL 



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. 1 B). 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 



