of tlie FisJiery Board for Scotland. 125 



With a view to testing the theory respecting this group (III.) a numher 

 of creels were shot during March to August in 1900 and 1901. They 

 were set just outside low-water mark and were occasionally left dry by the 

 ebb. Some of the creels were at times shot in 2 or 3 fathoms. One or 

 two of the creels were covered with siuall-meshed netting. The number 

 and sizes of the crabs got in. each month are set out in Table II. 



In March and April very few crabs were got. This was in part due 

 to the fact that at that period "of the year it often hai)pens that bad 

 weather prevents fishing for a considerable time, but this does not account 

 for the small catches. Because even when the creels were fishing, it very 

 often happened that no crab was caught. Their absence from the creels 

 does not necessarily mean their absence from the region. They may not 

 then feed eagerly. Crabs that are kept in the Laboratory during winter 

 became very inactive. The cold has a much more paralysing effect on 

 the edible crab than it has on Carcinus moinas, so that it is ])ossible 

 that the inshore crabs may not move about much before the month of May. 

 In this month (May) a considerable number of crabs were got in the creels 

 shot in the same place as in the preceding months. (Vide Table II.) 



An examination of the catch of crabs shows that it consists of a large 

 number of crabs which fall into the gap between the Beach and the 

 Adult groups, but it also contains a large proportion of adult crabs. The 

 adult crabs appeared in the catches all through the summer. 



The curve formed by the measurements of these crabs has been intro- 

 duced into a chart along with the curves of the Beach and Adult crabs. 

 The latter are taken from my previous paper (Tables VIII a and IX.) 



A reference to the chart shows that the new group (red curve) tends to 

 fill up the gap between the two former groups. The curve overlaps both 

 groups. It measures from about 2 inches to over 7 inches. The examina- 

 tion of the shore waters was not carried on during the whole of the year, 

 and the inshore migration of the adult crabs introduces larger crabs 

 than actually belong to the group under consideration. 



We then have in the summer in the shallow inshore water a double 

 group, consisting of the III. and IV. groups. In the autumn and winter, 

 investigation will veryprobably show that the adult group will be entirely, 

 or almost entirely, absent, and in these seasons, therefore, a better defined 

 Group III. should be found. 



Rate of Growth. — As material for the study of the rate of growth of 

 the crab, I have introduced here the measurements of the monthly collec- 

 tions made on the beach at Dunbar (Table III.), and also the details 

 of the individual catches which were measured (Table V.). The totals 

 were given in my former paper, and the regions where the catches were 

 made are in certain instances given in Table V. I have also introduced 

 three additional collections made on the beach, Dunbar, in 1899 and 1900 

 (Table IV.). 



Mr H. T. Waddington, Bournemouth, has kindly furnished me with 

 particulars of two series of casts of this form. The various ecdyses 

 which the two specimens underwent have been carefully recorded by him, 

 and he has permitted me to publish them here (Table VI.). The 

 measurements of the successive casts of a third crab, which were presented 

 by Mr. Waddington to Professor Howes, were kindly supplied to me by 

 Mr. William Wallace, B.Sc, Lowestoft. 



Specimen A. when captured, viz., in August, measured 3*25 mm.; it 

 had probably been in the megalops stage not more than a month 

 previously. When one year old it measured 30*75 mm., i.e., 1| inches ; 

 when two years old it measured nearly 46 mm., i.e., a little less than 

 2 inches across. Assuming that the rate of growth in nature approxi- 

 mated to the data here given, we should conclude that the beach group con- 

 sisted of crabs in their second year, and that a crab of 4^ inches across 

 would be not less than three years, nor probably more than four years old. 



