of the Fishery Board for Scotland, 



81 



mature crabs at the different sizes ; further investigation is required 

 ere this could be satisfactorily accomplished. While it is not im- 

 possible that the crabs on the Northumberland coast become mature at 

 a later stage than those off Dunbar, I think it highly improbable. The 

 conclusion, so far as the berried crabs and those with empty egg- 

 capsules are concerned, then, is that the female crab may be mature 

 at the size of 4£ inches, and that a large proportion of the crabs are 

 mature between 5 and 6 inches. 



With regard to the second character, viz., the development of the 

 ovary, it may be granted that when the ovary is ripe the crab will 

 carry eggs before it casts ; in other words, before it increases in size. 

 Herrick,* however, has recorded two cases where the lobster had 

 extruded its eggs immediately after casting. He regards such a process 

 as extremely rare. The ovary must have been ripe at the time of 

 casting. No analogous case in the crab has come under my observa- 

 tion. This contingency may, I think, be neglected ; the presence of a 

 ripening ovary may be regarded as a proof of maturity. Wilson,f from 

 his examination of the ovaries, states that " nearly all the large and 

 hard autumn crabs are ripe, or almost ripe ; whereas, though, as I have 

 found, crabs in a similar condition occur at other times of the year, 

 they are proportionately few." In a ripe ovary all the eggs are not of 

 one size, The diameter of the yolk mass may vary from ■3- , 41mm. ; 

 in some eggs the yolk sphere is as small as , 24mm. The diameter of 

 the zona radiata varies greatly from the fact that the egg in the ovary 

 has a large perivitelline space. In the egg, when carried on the 

 swimmerets, the perivitelline space is very slight. In the ovary the 

 diameter of the capsule may vary from '44-*7inm, The eggs are 

 slightly oval. The external eggs measure — outer capsule, , 44x*41, 

 •45x-45, -44x-46, -51x*48; egg sphere, -4x-4, '38 x '4, -4x'38, 

 •42 x *42. The ripe ovary is of a turkey-red colour. It is very much 

 distended, and covers almost the whole dorsal surface of the body of the 

 crab. It contains a large quantity of an amber-coloured fluid. I have 

 not met with a ripe ovary in a crab at any other time than autumn 

 and winter. The unripe ovary is of a pale colour, with often a 

 slight greenish tinge. It contains small unyolked eggs on an average 

 about 'lmm. in diameter. The eggs become yolked when about ^mm. 

 in diameter, and in consequence the ovary assumes an orange colour, 

 at other times pink or red. Yolked eggs of *2 and -24mm. diameter 

 are found also in white ovaries. The so-called coral condition of the 

 ovary is not an indication of ripeness. In each month of the year, 

 with the exception of March, April, and September, when I have not 

 dissected any crab, I have found the ovary with yolked eggs, and 

 consequently coloured either orange or red. An analysis of a number 

 of crabs with respect to the condition of the ovary and the size of the 

 eggs is given in the Table on p. 90. They are arranged in the months 

 during which they .were obtained and examined. The presence of a 

 coloured ovary is, then, an indication of maturity. The developing 

 ovary is very seldom found in a soft crab. A fc-jft crab in August, 

 measuring 5-| inches had an orange-coloured ovary, with eggs of 

 about *15mm. That was the only case in which other than a pale 

 white organ was found before the crab had become hard. While 

 the number of hard crabs examined was large, they are not of sufficient 

 diversity in size to afford much evidence on the question of the smallest 



* "The American Lobster : a Study of its Habits and Development." Bulletin U.S. 

 Fish Commission for 1895, p. 35. 

 t Op. cit., p. 4. 



