98 MR J. T. CUNNINGHAM ON THE 



autumn, in August and September. The eggs which I studied were obtained 

 in August off the Longstone Lighthouse, Fearn Islands. 



Embryonic Period and Temperature. — Hatching took place on the eighth 

 and ninth days, the temperature varying from 11°5 to 14° - 5 C. 



In the herring ovum the yolk consists of a number of nearly spherical 

 translucent vitelline globules ; there are no oil globules. The blastodisc is 

 large in proportion to the yolk. 



Diagnosis of Larva. — The length of the newly hatched larva is 5"2 to 53 mm., 

 according to Kupffer. The mouth is open, the body is wholly transparent 

 except the eyes, which are of a deep black, and perfectly opaque ; there are no 

 red blood corpuscles; the notochord is unicolumnar ; the anus is at a distance 

 from the yolk sac, being 1 mm. from the end of the tail; the pectoral fin is 

 present as a simicircular fold of membrane ; the pelvic fin is not developed ; 

 compact chromatophores are present on the sides of the body and tail. 



The larva? of the herring I have taken occasionally, but not often, in the tow- 

 net. Two were obtained at 5 fathoms depth west of Inchkeith, Oct. 7, 1885 ; 

 15 at a depth of 3 feet off St Abb's Head, Sept. 30, 1885 ; a few at 3 fathoms 

 east of Inchkeith, May 14, 1885; and a few at 5 fathoms north-east of Inch- 

 keith, April 15, 1885. 



2. Salmo levenensis (Loch Leven Trout) (PI. I. fig. 4). 



This figure is taken from an alevin of the species obtained from Sir James 

 Maitland's hatchery at Howietoun. The larva was three days old ; the per- 

 manent anterior dorsal, caudal, and anal fins have begun to develop, but the 

 median larval fold is present behind the anterior dorsal, behind the anal, 

 and between the anus and the yolk. The pelvic fins have appeared; they are 

 situated some distance in front of the anus, and they have no connection with 

 the preanal larval fin, which extends between them up to the yolk sac. 



3. Osmerus eperlanus, Lacdp (Smelt or Sperling) (PL I. figs. 5, 6). 



The mature egg of Osmerus, when first shed, is yellow in colour, and but 

 slightly translucent ; it is surrounded by a double zona radiata, the inner 

 surface of which is, as in all Teleosteans, in immediate contact with the vitellus. 

 When the eggs are allowed to fall on to stones or glass plates in water contain- 

 ing milt, they become attached and fertilised simultaneously. The attachment 

 is effected in the following manner : — The outer zona radiata ruptures at the 

 region of the ovum which is opposite the micropyle, and peals off the inner 

 zona, becoming of course inverted in the process. Over a circular area sur- 

 rounding the micropyle, the two layers of the zona remain firmly united. The 



