THE GROWTH OF CERATIAS HOLBOLLI 19 



allometry to enantiomeric (i.e. absolute negative) growth. From this point onwards during ontogeny 

 the absolute size of the caruncles decreases. 



True negative growth of this kind has been observed, for instance, in the abdominal limbs of crabs at, 

 and shortly after, metamorphosis (Huxley & Teissier, 1936). The association in this instance with 

 metamorphosis, and its abrupt and unique occurrence in the growth pattern of C. holbolli, suggests that 

 the onset of enantiometry betrays a crisis in the development of the organism. In C. holbolli this crisis 

 is most likely to be sexual maturity which would then be attained when the fish reaches 12 cm. standard 

 length. Bertelsen (1943, p. 202, fig. 5) divides adult specimens of C. holbolli from juveniles at the 

 presumably arbitrary figure of 15 cm. total length, and it is interesting that this value should virtually 

 correspond with the one obtained from the log log curve. 



If enantiometry of the caruncles does indeed coincide with sexual maturity, then these organs 

 probably have some kind of sexual significance. Rauther (1941) has shown that the caruncles are 

 luminous. In the darkness of the deep sea it is to be supposed that the female C. holbolli possesses 

 some luminous device to which the free-swimming males of the species may be instinctively attracted. 

 Parr (1932) suggested that the illicial esca might attract in this way. Now Waterman (1948), considering 

 the Ceratioidea generally, has further discussed Parr's suggestion, and has pointed out that, since the 

 structure of the esca differs considerably between, and even within, many genera of Ceratioids, the 

 free-swimming males may thus have been enabled to discriminate between females of different genera 

 or species. The objection to this view in C. holbolli is, of course, that the male is likely to be swallowed 

 as prey by the blind female, unless the latter possesses chemoreceptors capable of detecting the proximity 

 of a male. In the seeing Ceratioid Gigantactis this arrangement is possible, since Brauer (1908) has 

 found sensory endings in the esca which are apparently gustatory ; moreover, Waterman has stressed 

 the considerable sensory innervation of the esca in this form. But these sensory nerves are most 

 likely associated with the bunch of filaments characterizing the esca of Gigantactis, whereas in Ceratias 

 holbolli the filaments are reduced to a vestige. Also Gigantactis lacks caruncles which are a feature 

 peculiar to the Ceratiidae. It is probable, therefore, that here the caruncles, and not the esca, function 

 as the luminous recognition mark for the male. Beebe & Crane (1947) observed a moribund specimen 

 of ' Mancalias iiranoscopns ' immediately after capture, and noted that the caruncles moved slowly back 

 and forth alternately. So it may be that luminosity of the caruncles is combined with a characteristic 

 signalling movement. 



Since the caruncles may be supposed to reach their absolute maximum size and presumably maximum 

 luminosity at sexual maturity, it follows that the males would have the best chance of finding the 

 females round about that time. A male is therefore likely to become attached early in the female's 

 sexual life, but her chance of securing a male after sexual maturity would become progressively smaller 

 as she grows larger. In this respect it is interesting that, among the fourteen individuals over 12 cm. 

 standard length, and therefore supposedly adult (Table 3), only three had dwarfed males attached to 

 them. 



The change in shape of the caruncle during ontogeny is shown in Fig. 2 A, B and C. In the juvenile 

 there is a marked differentiation into a head and a stalked region. At a later period, presumably after the 

 onset of enantiometry, the club shape becomes progressively less pronounced, until the aged individual 

 may bear completely sessile caruncles which are reduced to mere black prominences among the spines 

 of the back. Fig. 2 also shows how the caruncles become gradually separated as growth proceeds, 

 although the right caruncle always remains slightly anterior to the left. Terminal pores are apparently 

 characteristic of the caruncles at all stages, since they were present in all the four specimens I 

 examined (nos. 1, 5, 9 and 12). They suggest an open type of luminous gland, resembling that of 

 the esca. 



3-= 



