Holt — On the Eggs and Larvce of Teleosteans. 439 



the notochordal region, thus differing from the condition shown in Brook's newly- 

 hatched larva {op cit., pi. 6, fig. 27). Thereafter the black pigment of this region 

 tends to become . concentrated into two bars — one midway along the post-anal 

 region, and the other above the anus, sending dendritic lines on to the dorsal fin 

 which apparently mark the site of the future first permanent dorsal fin (fig. 38, d. i.). 

 This is the condition when the postlarval condition is reached (fig. 38) when all 

 yellow pigment has disappeared, except three patches along the margin of the 

 embryonic-dorsal fin. The eyes are black, and the roof of the abdomen and the 

 rectum are profusely pigmented. There is, thus, at this stage, no practical 

 difference from the condition shown in Brook's figure of an embryo of three days 

 {op. cit., pi. 6, fig. 29). 



The most interesting condition in this form is the development of the paired 

 fins. At a comparatively early stage (fig. 15) what appears to be a fold of epiblast 

 is pushed out from the lateral region of the embryo, occupying about the middle- 

 third of the pre-anal length, and never, as far as can be seen, extending back to 

 the region of the embrj^onic-ventral fin. The anterior and posterior portions of 

 this fold develop rapidly, forming a couple of slight prominences connected by a 

 narrow ridge (c. r.). The prominences represent the pectoral (p.f.) and pelvic {pl.f.) 

 fins, which thus, at their earliest stage, are connected by a continuous epiblastic 

 ridge, which may even be regarded, as Balfour suggests in Elasmobranchs,* as a 

 continuous lateral fin. 



Though at first equal, f the pectoral soon outstrips the pelvic fin in develop- 

 ment, and the connecting ridge disapjDoars or becomes very inconspicuous. At 

 hatching (fig. 37) the pelvic {pl.f.) still retains its original position behind the 

 pectoral {p-f.), the bases of the two being in the same straight line. As the yolk 

 is absorbed, the pectoral undergoes the usual rotation, and is carried downwards 

 and forwards to the clavicular region (fig. 38, p./.), whilst the pelvic {p>l-f-), now 

 growing more rapidly, is similarly rotated, and travels downwards and forwards 

 to a ventral position a little behind the pectoral ; the assumption of the jugular 

 position is a feature of later development. 



From Brook's account ('' L. S. Journal," vol. xviii., p. 298) it appears that the 

 pelvic fins appear very early in Motella mustela, though this was not noticed by 

 M'Intosh and Prince {op. cit.) in the same species, nor by Raffaele {op. cii.) in 

 Motella tricirrata. 



Pelvic fins do not appear till much later in all other Teleosteans with pelagic 

 ova, of which the development has been studied. 



* " Comparatiye Emtryology," vol. ii., p. 6-11. 



t Brook speaks of the pelvic fins as appearing later tlian the pectoral, but both, fins seemed to me to be 

 developed at the same time. 



