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Part III. — Twenty-first Annual Report 



collateral evidence furnished by the examination of berried females 

 indicates that hatching takes place over a considerable portion of the 

 year. 



The eggs hatched in the Laboratory on two occasions, viz. in May and 

 July. 



Several females spawned in the Laboratory at the end of September 

 and in October. 



The Egg. When first extruded, the eggs are in the mass of a light 

 orange colour ; the single egg is straw-coloured. The eggs are nearly 

 circular ; some are oval. Four eggs measured as follows, -375 : '37 : "37 : 

 •35 X •4 mm. 



As development proceeds, the colour of the egg changes to a deep 

 amber. 



When the eggs are ready to hatch the amber colour has disappeared, 

 and the mass is of a dirty grey colour. The change from the amber 

 to the grey takes place not very long before hatching, probably within 

 a month. 



The length of the period of incubation is not known. Meek suggests 

 four months. This is very probably not an over-estimate. 



Berried females may be got on the beach between tidemarks during 

 nearly the whole year. The eggs on different females are in different 

 stages of development, which indicates a more or less extended spawn- 

 ing season. 



In January at Dunbar the eggs of a female were of a dark amber 

 colour, and the eyes were present in the embryo. 



In April twenty-three females were examined at Dunbar. On the 

 majority of these the eggs were of a dirty grey colour (ready to hatch) 

 in five or six the eggs were of a light orange tinge. 



In May a considerable number have been examined at Dunbar and 

 at the Bay of Nigg. One measuring 6 cm. across had eggs ready 

 to hatch, and another 4 cm. had advanced eggs; seven had eggs of 

 a light amber colour, and one of these measured just under 4 cm. in 

 breadth. Of several crabs sent from the Dornoch Firth, two had 

 orange eggs, while in the case of the others, hatching was proceeding. 

 In a lot examined at the Bay of Nigg during this month the smaller 

 females had advanced eggs, the larger had orange -coloured eggs. 



In June at Dunbar one of those found had eggs ready to hatch, half- 

 a-dozen others had orange eggs. 



In July the eggs hatched in the Laboratory. 



In September, a female 6 cm. was found carrying advanced eg 

 the eyes were formed. 



Females have been found with empty egg capsules attached in con 

 siderable quantity to the swimmerets in May, June, and August 

 These crabs had hatched their eggs shortly before capture. 



These facts then indicate that the hatching of Carcinus occurs over a 

 long period, viz. from April to end of July. Du Cane found that the 

 eggs hatched in March. In putting the period during which the Zoea 

 of this crab may be found as from March to end of July, I do not 

 think an over-estimate is made. 



The fact moreover that crabs having eggs ready to hatch, while others 

 carry eggs which will not hatch for some time, are got simultaneously 

 points to an extended spawning season. 



The spawning season of Cancer pagurus lasts three months, viz. 

 November, December, and January. Hatching of this form took place 

 at Dunbar in July and August, and at Bay of Nigg, August and 

 September (end of). In 1902, while the eggs of certain of these crabs 

 were hatching, the eggs of other individuals were still red. 



