of the Fishery Board for Scotland. 



243 



1 basin. Length up to 10 mm. Temperature, surface +10° R.j sp. gr. 

 4 1-027. 



* May 23. Fry remain most frequently in shade — in the east end of 

 4 the basin in the morning, and the west in the evening. 



1 Differences in she of fry is very considerable, while stage of develop- 

 1 ment is almost the same for all, the size of the different breeds already 

 1 making itself felt. 



4 June 3. Fry a month in the basin. 50 specimens caught to be preserved 

 4 in spirit; length from 16 to 9 mm. The smallest did not seem to have 

 4 reached the same stage of development as the larger ones. The fry are 

 4 to be found over nearly the whole basin. The east end appears to be 

 4 their favourite place at all times of the day, or it may be that they are 

 1 better seen on the background of the lighter bottom. 



4 8. In course of the last two days the number of the fry seem to have 

 4 considerably decreased, but possibly this is only apparent. I saw a 

 4 young cod right down on the bottom in 2 fathoms of water. 



4 10. After the most careful observation, I have come to the conclusion 

 4 that the cod fry attack and eat each other in considerable numbers, while 

 4 the larvae of the crabs (both in the zoea and the megalops stage) are 

 4 almost never pursued, and, as far as I have observed, never caught. The 

 4 cod fry seem not to lack the will to attack, but the young crabs are 

 4 excellent swimmers, and manage to get away. On the other hand, they 

 4 do not seek to attack the cod fry, and at first it seems as if they would 

 4 be able to grow up together. But the crabs will pretty certainly, in the 

 4 long run, fall a prey to the cod, when the difference in size is more con- 

 4 siderable than at present. 



' As the cod, at least when they are larger, seldom attack individuals of 

 4 their own species, their present rapacity may possibly be due to the fact 

 4 that the basin, which is new, and consequently poorly supplied with 

 1 plants, has too little means of nourishment in proportion to the number 

 4 of fish. I made another attempt to feed them, and with some success, 

 * as some individuals swallowed pieces of fine-scraped mackerel. 



4 19. In the course of the last few days several fry have been examined, 

 4 and the stomach has been found full of various sorts of small crustacea, 

 4 and the larvae and pupae of flies, of which there are enormous numbers in 

 4 the basin, and also of the food now daily thrown into the pond. The east 

 4 end of the basin, which consists mainly of sand, seems to be their favourite 

 ' place at all times of the day. To-day I tried if they would eat fine- 

 4 chopped mussels, fine-scraped fish, &c, but in vain. They fled with all 

 4 haste.' 



The following paragraphs relate to the rate of growth of the young 

 cod : — 



4 When the young come out of the egg it has a length of about 3 mm. 

 4 In course of the first eight days, while the yolk gives continual nourish- 

 4 ment, it increases 2 mm., so that it has a length of 5 mm. when taken 

 4 out of the apparatus. 



4 The further growth is extremely diverse in the several individuals, 

 4 which may depend on difference of race as well as on the greater or less 

 4 quantity of food the young creature manages to procure, and consequently, 

 4 when I give a size, it must be understood as an average. 



4 Between 6th June and 8th July there is a great spurt in the develop- 

 4 ment, which may be explained by the fact that the young begin to eat 

 4 the food flung to them in considerable quantity twice a day. 



4 From middle of October to the middle of February the growth has 

 4 been much slower, for reasons which are very easily explained. The fry 

 4 of the cod in the open sea set out for deep water when the surface water 



