DEVELOPMENT AND LIFE- HISTORIES OF TELEOSTEAN FISHES. 853 



No form hitherto examined shows this double frill so well, a feature probably connected 

 with the peculiar condition of the ventral surface of the abdomen. In relation to the 

 latter, we have immediately below the small and vertically elongated pectorals a spherical 

 body, the liver, then a smaller mass (gut ?), and lastly the large ovoid swelling of the 

 yolk, which is closely applied to the gut above and to the rectum behind. The latter is 

 well marked, and appears to open by an anus at the tip. 



Unfortunately the preservation of this specimen was defective and the sections unsatis- 

 factory, but one feature of note was observable, viz., the fact that the yolk contained a 

 large oil-globule surrounded by a belt of protoplasm in which were a series of small 

 oil-globules, which thus formed a ring round the larger central one. The lateral fold on 

 each side of the yolk showed epiblast outside a core of intruding mesoblast. 



Certain features in this form approach those of the larval Arnoglossi, described by Dr 

 Raffaele (125a, pp. 49-55). Zeugopterus, Rhombus Icevis, and probably other Pleuro- 

 nectids, however, also have an oil-globule in the egg. 



Ovum of Pleuronectid (B) — with large peri vitelline space. — This large ovum, 

 frequently met with in the trawling expeditions of 1884, and every year since, 

 is characterised by its large peri vitelline space, in which the yolk with the early blastoderm 

 floats freely like a globule. At a later stage (PL XIII. fig. 3) the yolk keeps the 

 upper arch of the egg with the embryo curved beneath. The zona radiata is com- 

 paratively thin, and it is sometimes difficult to obtain a clear view of the minute 

 punctures (PI. X. fig. 8). It is, however, not devoid of toughness. The contained 

 embryo shows chrome-yellow and blackish chromatophores, the former extending nearly 

 to the tip of the notochord. The newly hatched larval fish has been figured and described 

 elsewhere,* so that it is only necessary to mention the later stages. The larval fish 

 during the absorption of the yolk often shows prominent processes projecting from the 

 surface of the yolk into the anterior space. When the yolk has been absorbed the fish 

 presents three distinct yellowish bars behind the vent (PI. XVIII. fig. 2), another at the 

 latter (vent), and a line along the dorsum of the intestine, besides various touches of the 

 same on the head and elsewhere. Stellate black pigment-corpuscles occur along with the 

 yellow, and in the early condition are present over the yolk. The eyes soon assume a 

 silvery aspect. The larval fish is active and comparatively large, resembling in certain 

 respects the plaice. It is probably a pleuronectid. 



Mr Cunningham describes the same egg before hatching.t It is not uncommon both 

 in St Andrews Bay and in the open sea beyond. 



Unknown Ovum (C). — Besides the foregoing, a small undetermined ovum occurred in 

 the mid-water net in April, and probably belongs to the same group (Pleuronectidse). 

 The contained embryo is comparatively large and fills up the capsule almost completely. 

 The larva issuing from this egg is represented in fig. 1, PI. XVIII., the dull brownish- 

 yellow pigment being characteristic. Moreover, the mouth of the embryo is open at the 

 period of hatching — as in the plaice. 



* Vide Seventh Annual Report, Fishery Board for Scotland, 1889. t Op. cit., p. 105, pi. vii. fig. 2. 



