of the Fishery Board for Scotland. 9 



were collected, the number in April being nearly sixteen millions, 

 and in February nearly twelve millions. It may be stated that 

 the collection of eggs extends over a longer period at the Bay of 

 Nigg than was the case at Dunbar, where the work did not usually 

 ommence until March, the average duration at the former being 

 65 days and at the latter 86 days. The difference is due, not to 

 variation in the spawning season, but to the circumstance that the 

 fishes at Dunbar, being for the most part collected a little before 

 the spawning, did not become accustomed to confinement suffi- 

 ciently to part with their eggs until the spawning season was some 

 way advanced, while at the Bay of Nigg they are kept in the large 

 pond throughout the year, and spawn under natural conditions 

 approximately during the same time that plaice are found spawning 

 in the sea. An abundant supply of pure sea-water, of suitable 

 temperature and specific gravity, has materially aided in the success 

 of the work ; and as mentioned in last year's Eeport, the cost of the 

 fish hatching, when the hatchery is operated in conjunction with 

 the Marine Laboratory, is materially reduced, and does not exceed 

 £100 per annum. 



The period for which the embryonic and larval fishes are pro- 

 tected in the hatching apparatus amounts to about half the 

 duration of their pelagic life, but the benefit would be considerably 

 increased if it were possible to rear them in any large numbers 

 through their post-larval stages — that is, until they have completed 

 their transformation and become adapted to live on the bottom. 

 The rearing is not an easy matter, owing to the difficulty of pro- 

 viding suitable food for multitudes of larvfe confined in relatively 

 small volumes of water, but the attempt to do so will be made by 

 the use of a special tank. 



Since the hatchery was established the number of fry of the food 

 fishes which have been produced is as follows: — Plaice, 340,455,000 ; 

 lemon soles, 5,727,000 ; turbot, 5,160,000 ; cod, 4,010,000 ; and other 

 kinds, 2,000,000— the aggregate being 357,352,000. 



During the season deputations of fishermen from Aberdeenshire, 

 who visited the establishment by arrangement with the Technical 

 Education Committee of the County Council, received demonstra- 

 tions as to the operations and the life-histories of the food fishes. 



The Life-Histoey of the Ckab. 



In the present Eeporfc will be found a paper, illustrated by four 

 plates, in which Dr. H. C. Williamson gives the results of further 

 observations on the life-history of the edible crab and some other 

 Decapod Crustacea. The observations deal mainly with the repro- 

 duction, and in this connection with the processes of casting, 

 impregnation, and spawning. The spawning of the crab takes place 

 in November, December, and January, and the casting of the shell 

 and impregnation take place in summer : and it appears probable 

 that in most cases spawning does not follow until about fourteen 

 or fifteen months after the process of casting. 



On extrusion the eggs are attached to the swimmerets of the 

 mother, and remain there for about seven months. The mode by 

 which the eggs are attached is of interest, the author having 



