100 



Whetlier these unchanged ova would have developed subsequently to the 

 bu^th of the present superficial layers of embryos, or whether they were destined 

 for the intra-ovarian nourishment of the present embryos, are questions which 

 it is impossible in an isolated case to discuss ; but from their large size, which 

 precludes any suggestion of immaturity, it would seem probable that they were 

 intended for present use rather than for a future brood. 



The embryos, which are long and eel-hke — 6 to 8 millim. long — lie matted 

 together, firmly adhering to one another by their tails, by means of a coagulated 

 secretion. 



The vertical fins only are represented by a median fold of integument, which 

 runs fi'om the occiput, round the tip of the tail, to the vent. This fold of integu- 

 ment consists of very numerous layers of large-nucleated cells. The remains 

 of the yolk-sac are enclosed in the abdomen, causing a bulging of the abdominal 

 wall along its whole length, from the throat to the vent ; but there is no vitelline 

 constriction or pedicle. 



I am inclined to think that the vertical fold of the integument, which is 

 really only an extended sheet of embryonic cells, is an absorbent (nutritive) 

 surface, somewhat as in the embryos of certain fishes of the family EmUotocidx, 

 in which the interradial membranes of the vertical fins have been shown to act 

 as a foetal placenta. 



In the present case, however, there is no vascular connexion, at any rate on 

 the foetal side ; and I am inclined to think that the nutrient material is absorbed 

 not so much from the thin tough ovarian capsule as from the ovary itself, perhaps 

 from those ova in which no trace of a germinal vesicle can be found. 



An embryo taken at random measures 8 millim., namely 2 millim fi'om the 

 snout to the vent and 6 millim. from the vent to the tip of the tail. 



78. Dlplacaiithopoma hraelifjsonia, Gimther. 



DipZacanf/iopoma Z^rac?)j/soma, Giinther, Challenger Deep Sea Fishes, p. 115, pi. xxiii. fig. C: Goode & Bean, 

 Oceanic Ichthyology p. 319: Alcnck, Illustrations of the Zoology of the Investigator, Fishes, pl. XVII, 

 FIG. 2, [s'pecimen with an injured tail). ^- 



Differs from B. Rivers- Andersoni only in the following particulars : — 



The branchiostegal rays appear to be only six in number. 



The snout, though otherwise similar, is only as long as the eye. 



The diameter of the eye is nearly a foi;rth that of the head. 



The distance between the ist anal ray and the axilla is less than the length 

 of the head. 



The ventral fins arise nearer to the clavicular symphysis : though stout, they 

 are not fluted. 



