of the Fishery Board for Scotland. Li 
with the laboratory. Apart from the cost of the distribution of 
the fry, the expenditure on the hatching work is now under £100 
per annum, and the total expenditure does not greatly exceed 
that sum. 
Besides the hatching of the plaice above referred to, the hatching 
of lobsters and crabs was also undertaken by Dr. H. C. Williamson 
at the request of the fishermen on the coast of Aberdeenshire. 
Abont 4,500,000 larvee of the crab, and three thousand young 
lobsters—most of which were reared through several stages, and in 
some cases nearly to the stage at which the adult form is assumed— 
were liberated along the coasts of Aberdeen and Banffshire. In the 
case of the plaice, it may be explained, the time during which the 
embryonic and larval fishes are protected extends to about half the 
period of their pelagic life, at the end of which they settle on the 
bottom as young flat-fishes. 
Since the hatchery was established the number of the fry of 
the food fishes which have been produced at it amounts to 
303,752,000—viz., 286,855,000 plaice, 5,727,000 lemon soles, 
5,160,000 turbot, 4,010,000 cod, and 2,000,000 of others. Of the 
plaice, 136,065,000 were produced at Dunbar, when the hatchery 
was situated there, and 150,790,000 at the Bay of Nigg since 1900. 
Tue DEVELOPMENT OF THE CRAB. 
The present Report also contains a paper by Dr. H. C. William- 
son on the larval and early young stages of the common shore 
crab (Carcinus meenas), in which the developmental changes that 
occur are traced with great care and minuteness. It is comple- 
mentary to another paper on the edible crab contributed by the 
same naturalist to the Nineteenth Annual Report. The character 
and structure of the various appendages in the Zoéa stages and in 
the Megalops are fully described and illustrated by a large series 
of figures, and the features which distinguish these stages from the 
corresponding stages of other forms are detailed. The development 
of the branchiz or gills is very fully treated. A number of obser- 
vations were also made in regard to the reproduction, the rate of 
growth, and the moulting of the crustacean in question. The 
duration of the period of incubation of the eggs has not yet been 
determined, but it probably exceeds four months. 
The period of hatching extends over a considerable number of 
months—viz., from March to the end of July—and_berried 
females may be got on the beach between tide-marks during nearly 
the whole year with the eggs of different females in very different 
stages of development. The eggs are at first straw-coloured, 
becoming deep-amber as development proceeds, and dirty-grey 
before hatching. The larval crab leaves the egg in the so-called 
Protozoéa stage, which is transitory, the delicate integument being 
immediately cast, and it then appears as a Zoéa, of which there are 
four stages, each following a moulting. At this time it is wholly 
pelagic, or free-swimming, a mode of life which appears to last for 
about a month or a little less. The next moult gives rise to the 
