of the Fishery Board for Scotland. 



85 



purposes still immature. They will therefore probably cast again the 

 next year. In those crabs which are fertilised the ovaries will develop, 

 in response to the stimulus supplied by the presence of the sperms in 

 the spermatheca. As to how long an interval elapses between casting 

 and the extrusion of the eggs my evidence is not complete. But, 

 while a large number of the crabs will not become berried until at 

 least about 12 months after they have cast, still there is a certain 

 amount of evidence that a crab may extrude its eggs in the winter 

 immediately following the summer when it cast. A number of soft crabs 

 were kept in confinement at Dunbar from September 25th till early in 

 December. They were, with the exception of one (5f inches), over 5| 

 inches in breadth. Two of these crabs, 5g and 7J inches, were on 9th 

 December not quite hard ; the former had a white ovary with yolked 

 eggs measuring '2mm. in diameter ; in the latter the ovary was orange- 

 coloured and contained eggs *2 and "24mm. Certain crabs which are 

 hard, of clean appearance, and white on the under surface, are known 

 as "China crabs"; they are got towards the end of the year, and are, 

 without doubt, crabs which have cast during the summer. One of these 

 examined in December was inches across, and had a scarlet ovary 

 with eggs -35mm., that is to say, very near, if not quite, ripe, and 

 certainly as large as many of the eggs in a ripe ovary. Another of the 

 same, measuring 6/^-, showed a pink ovary, with eggs "15 and '24mm. 

 in diameter. Many of the casters of one year are certainly not berried 

 until the winter of the following year. During the summer following 

 the cast they are found to be clean and light-coloured, and with 

 coloured developing ovaries, which will be ripe in the succeeding 

 October. Several of these clean crabs were obtained in May and others 

 in July. They were placed in the tanks at Dunbar, and of the 

 survivors one was berried in November; another was ripe in December, 

 but was killed before it extruded its eggs ; a third had yolked eggs 

 •24 and -27mm. in diameter ; and a fourth, killed in February, was 

 ripe. ( Vide Table, pp. 92, 93.) The conditions of captivity were probably 

 not very favourable for spawning ; but, in any case, it is the fact 

 that many of the female crabs of mature size, which cast in any year, 

 are hard, full crabs, with ripening ovaries in the following summer, and 

 extrude their eggs in the winter ; that is to say, about 14 months after 

 casting. Those crabs which cast early in the year — in July, for 

 example—would be more likely, then, to have ripe ovaries at the end of 

 the year than those which cast in September. If now, for clearness, we 

 give an age to the crab of the mature group, expressed in a number of 

 months counted from its cast, we may conclude that certain crabs may 

 be berried in six months, while others are not berried until over twelve 

 months afterwards. 



Annual Spawning. 



A crab does not always cast immediately it hatches its eggs. 

 It very often carries eggs two years in succession. The supply of 

 sperms which it receives when soft is not all used up in fertilising the 

 first batch of eggs, and so long as the sperms are present in the sper- 

 matheca the crabs will probably not cast. In fact, everything points to 

 the probability of the crab usually carrying two batches at least before 

 it casts again. This is demonstrated by an examination of those crabs 

 which are berried and those which have recently hatched their eggs. The 

 particulars of a number of these crabs will be found in Table II., p. 94. 

 The ovary of a berried crab just after it has extruded its eggs is small 

 and pale in colour, a slight greenish tinge being, however, sometimes 

 noticed. The eggs are small, transparent, non-yolked, about -1mm. in 



