of the Fishery Board for Scotland. 
327 
10. On the Developmext of the Lemon Dab (Pleuronedes microcephalus). 
The pelagic ova of this species first came under scientific observation in 
August 1884, when ripe females were procured off the Forth in the trawling 
expeditions in connection with H.M. Trawling Commission. Consider- 
able latitude, however, must be given in regard to the spawning period, 
since in the south it is very much earlier than in the north. Thus Couch''^ 
states : — ' It is prepared for spawning early in February, and appears to 
' be amongst the most prolific of flat fishes, the lobes of the roe being 
* large, and extending back from the small abdominal cavity, compressed 
' but wide, almost to the tail.' Parnell,t again, observes: — 'They shed 
* their spawn some time during the month of April, after which they retire 
' to rocky ground, where they generally remain till the commencement of the 
* following year.' He thiTs connected the fish with a migratory instinct 
during the spawning season. Day gives May and June as the spawning 
period ; also adding that Thompson (Ireland) found one in roe in March, 
the precise condition of the ova, however, not being stated. At Plymouth 
Cunningham found the pelagic eggs in March, April, and May. % He readily 
hatched them in 1888 in ordinary vessels of sea water (just as the ova of 
the cod and many other forms were developed during the trawling expedi- 
tions), and the larvse lived about five days. He estimates the diameter of 
the egg at 1'36 to 1*44 mm., and describes the zona (his vitelline mem- 
brane) as showing ' a number of fine raised ridges, forming two systems 
* of parallel lines, which cross one another diagonally.' He gives the 
development of the embryo and the extrusion of the larvse on the 7th, or 
early on the 8th day, in April, as well as the changes up to the 4th day. 
In the Researches § a figure of the zona is given. 
Professor Ewart and Dr Fulton give a report on the examination of 617 
examples in regard to maturity, and conclude that this species spawns 
chiefly, and in the ofl'shore waters, in June. 
Mr Holt had frequent opportunities in the expedition off the West 
Coast of Ireland last year of observing ripe fishes and their ova, as well as 
at the St Andrews Laboratory ; and he gives a careful account of the 
structure of the zona.|| 
At St Andrews the ova have frequently been under observation. Thus, 
besides occurring in tow-nets, a large jar of the ripe eggs in sea water was 
forwarded by Captain Burn from one of his ships in May 1886, and 
again subsequently; while last year (1890) Dr Fulton arranged with Mr 
Scott, Mr Murray of Newhaven, and various fishery officers for several 
supplies of ripe eggs, which were safely transported to the laboratory, 
where they were readily hatched. 
The first series of living ova was received on the 9th July, having been 
fertilised at 8 p.m. on the 8th July. The second series was fertilised at 
7 A.M. on the 9th July, and received the same day. The third series was 
fertilised at sea on the 11th July, and received at 3 p.m. on the 12th. H 
All were in good condition, and the number in each case was considerable. 
The eggs of the lemon dab are comparatively small when contrasted 
with those of the plaice, being, as shown in the Researches, '053 in., and 
thus are somewhat less than the eggs of the gurnard. They have the 
* Vol. iii. p. 187. 
t Fishes of the Forth, p. 367, 1837. 
X Jour. Mar. Biol. Assoc., ser. i., N, S. No. I., p. 13, March 1889. 
§ Researches, pi. i. fig. 18. 
II Trans. Roy. Bub. Soc, vol. iv., new ser., p. 453, pi. xlviii. figs. 19-21 ; pi. 1. 
fig. 39. 
H A fourth series was sent by the master of the traAvler * Shamrock' on 14th July. 
