Holt — On the Eggs and Larvae of Teleosteans. 457 



Unidentified Pelagic Ova. 

 Species I. — Solea (?) 

 (PI. xLix., fig. 26 ; PI. L., figs. 34 and 35.) 



A single e^g (fig. 26) occurred in the surface-net, in Clew Bay, on the 1st 

 Jul J, 1890. The diameter is l"38mm. The embryo is somewhat advanced, but 

 has only a short free caudal growth. The zona presents no characters of special 

 interest, and the perivitelline space {p. s.) is small. The yolk [g.) has a peripheral 

 layer of clear segments or vesicles (c. v.), which appear somewhat smaller and 

 more numerous than those of Solea vulgaris. A number of oil-globules are present 

 about the periphery of the yolk mass. They are divisible into two sorts : — 

 (1) Very minute globules {o.g. 1), arranged in little groups in the immediate 

 vicinity of the embryo, viz. beneath the head and close to the sides of the anterior 

 third of the body, with the exception of one very small group near the posterior 

 extremity. (2) Larger globules of varying sizes (o. g. 2) scattered irregularly over 

 the general yolk surface. The lens is fully formed, but the otocysts are as yet not 

 visible. A few small black chromatophores occur on the head ; and bright-yellow 

 chromatophores are profusely scattered all over the embryo, and on the parts of the 

 yolk-sac immediately adjacent to the head and trunk. There is no pigment on 

 the rest of the yolk-sac. 



Four days later, on the morning of July 5th, the larva was observed to have 

 emerged. On the afternoon of the same day it presented the following appearance 

 (fig. 34). Total length 4*10 mm., of which '30 mm. is occupied by a precephalic 

 expansion (/.) of the marginal fin, to be hereafter described. The post-anal length 

 is 2'10 mm., the anus (a.) being thus slightly anterior to median. 



The cephalic contour is remarkable. The mid-brain {in. h.) is relatively 

 enormous, and projects forward in a blunt point, overhanging the downwardly 

 directed fore-brain (f.b.); the cerebral lobes are large and rounded ; the pineal 

 sac is scarcely visible, being masked by other structures. The eye is large, and is 

 antero-ventrally directed : its posterior moiety lies behind the hinder end of the 

 optic lobes (»«. b.), — a very unusual relationship. The cerebellar fold cannot be 

 distinguished, but the hind-brain (?«. o.) is very large and prominent. The elon- 

 gated inferiorly concave otocyst (ot.) lies close behind the eye. No mouth is 

 visible, but the branchial bars (5. b.) and slits can be distinguished. With the 

 protrusion of the brain, the anterior end of the notochord is carried forward. A 

 large vesicular expansion (f.) of the marginal fin extends forwards over the head, 

 in front of which it projects like a large bladder. By the aid of dorsal (fig. 35) 

 and profile (fig. 34) views its relationships can be pretty well made out. The 



