of the Fishery Board for Scotland. 



89 



slowly backwards and forwards, in this way facilitating the escape of 

 the larva?. The swimmerets seem to move independently of one 

 another ; the bunch of eggs attached to each swimmeret is sharply 

 separated from those on either side of it. This is not the condition in 

 the crab which has just extruded its ova. At that time the eggs form 

 a large spherical mass in which there is no sign of division between the 

 masses of eggs of the different swimmerets. 



During the progress of this research it was discovered that the 

 Fishery Board had not the power, which is possessed by the District 

 Committees in England, to permit the possession of berried crabs for 

 purposes other than for bait. A number of berried crabs were obtained 

 in ignorance of this difficulty, and the evidence which they bring to bear 

 upon the different questions treated has been incorporated in the paper. 



Number of Eggs of the Crab. 

 Spence Bate found in one she-crab 2,000,000 ova ; Buckland states, 

 as the result of a calculation made by his secretary, that the crab carries 

 no less than 1,441,000 eggs. An approximate calculation of the number 

 of eggs carried by different crabs is given below. The number varies 

 greatly with the individual. The method adopted in the estimation 

 was as follows. The swimmerets with the eggs attached were preserved 

 in spirit. They were then dried in a water bath and weighed. From the 

 weight thus obtained was subtracted the weight of the dried swimmerets 

 of a crab of the same size, but which was not berried. The weight of 

 the eggs was thus found approximately. The weight of the hardened 

 cement by which the eggs were attached to the swimmerets was 

 neglected. The number in a small weight of the eggs was counted, 

 and from that datum the total was deduced. 



The Number of Eggs carried Externally by different Crabs. 





Size of Crab. — Greatest 



Estimated Number of 





Breath. 



Eggs. 



1 



5| inches. 



460,000 



2 



53 



750,000 



3 



°TTT » 



1,010,000 



4 



6 „ 



940,000 



5 • 



6- 5 - 

 "19 >> 



1,480,000 



6 



711 



3,000,000 



From the data given above there appears to be an increase in the 

 number of eggs with an increase in the size of the crab. In the case 

 of two crabs measuring 5| inches, the numbers of eggs were found to 

 be 460,000 and 750,000 respectively, while in the crab inches in 

 breadth the number of the eggs attached to the abdomen was estimated 

 at about 3,000,000. Herrick * found that the larger lobsters carried a 

 far greater quantity of eggs than the smaller specimens. A lobster, 8 

 inches in length was found to have on an average 5000 eggs, while in 

 those measuring 15-19 inches 80,000 to 90,000 were observed in 

 certain examples, the averages in that range of size being 46,000 to 

 77,000 eggs. From an examination of 4645 berried females Herrick 

 deduced the following law : — " The numbers of eggs produced by female 

 lobsters at each reproductive period vary in a geometrical series, while 

 the lengths of the lobsters producing these eggs vary in an arithmetical 

 series." How far this law is applicable to the crab extended investiga- 

 tion is required to show. 

 * Op. cit, pp. 51, 52. 



