Gatty Marine Laboratory^ St. Andrews. 243 



deposit tlieir ova in the sand in December and January, and 

 probably somewliat later, so that a succession of larval forms 

 appears in March and April, and which, by-and-by assuming 

 the pelagic stage, become as they grow larger a very im- 

 portant element in the nourishment of the food-fishes of our 

 shores. 



2. On the Eggs and Young of the Pollack 

 (Gadus pollachius, L.) 



Some years ago* a few remarks were made on the spawning 

 period of this species. On the first occasion only preserved 

 ova were forwarded by the able assistant fishery officer at 

 Lerwick, Mr. Duthie, Ijut the following season lie sent a few 

 fresh ova in sea-water ; their condition, however, was unsatis- 

 factory. This energetic officer nevertheless has lost no oppor- 

 tunity of filling up the gap in regard to this and other species 

 requiring investigation. Since the foregoing remarks were 

 published Mr. Holt obtained two ripe females (in the spring 

 of 1891) off the west coast of Ireland, and, though no male 

 could be obtained, they were fertilized with the milt of a cod. 

 He found their diameter to be 1'13 millim. in the unfertilized 

 condition, a size they for the most part kept after formation 

 of the perivitelline space, though extremes ranged from I'lO 

 to 1'16 millim. Three days later they exhibited a very 

 translucent embryo, devoid of pigment and with no free caudal 

 region. He was unable to develop them further. 



This year Mr. Duthie with difficulty procured a few fer- 

 tilized ova on the 2nd May, and forwarded them at once. 

 Unfortunately they were delayed in transmission, probably 

 by the dense mist, and they only reached the laboratory 

 about 5 P.M. on the 6th, the majority having succumbed. 

 They measured 1*1430 millim., a size agreeing with that of 

 the green cod and with some that were sent in solution in 

 1893. These had the tail becoming free from the yolk, but the 

 condition was not quite normal, and the exterior of the capsule 

 was covered with debris in all. The blastopore had closed 

 and the tail was just commencing to extend beyond the yolk. 

 The optic vesicles were distinct and the auditory vesicles 

 were indicated by a minute clear ovoid area. Kupffer's 

 vesicle was present. Moreover, a series of black chromato- 

 phores occurred on the head and along the sides of the body 

 to the tail. The notochord appeared in the middle line, but 

 the muscle-plates were indistinct though probably present. 



• Tenth Annual Report, p. 288 (1892), and Eleventh Annual Report, 

 p. 246 (1893), 



18' 



