276 HISTORY OF THE LOBSTEB AND CRAB. 



hatch once and spawn once every year. It does not follow, however, 

 that this is continued every year without intermission. It proves 

 that it may and does happen in two successive years. 



%. — The Crab. 

 It is well-known that the young crab when first hatched from 

 the ^^^ has the form known as the Zoaea, which swims about freely 

 in the water. After a time, the Zoaea changes into the Megalopa, 

 which is also a swimming form, and this into the young crab, which 

 ceases to swim and walks about on the ground. Last summer I 

 was desirous of finding and capturing some of the little crabs 

 directly after the transformation, and as small crabs from J- inch 

 upwards are common between tide marks, I searched in August 

 and September for the still smaller specimens which must have 

 been produced from the Zoseas hatched in the summer. For some 

 time I could not find any small enough to be recognised as the new 

 season's brood, but while spending a few days at the Laboratory of 

 the Biological Association, at Plymouth, I obtained some specimens. 

 These specimens were lo in number, and were found among a 

 quantity of coralline brought from the shore of Wembury Bay 

 near the Mewstone. The smallest was 2 -5 mm. (VVh inch) across 

 the carapace, the largest 7 mm. (a little more than i-in.) The 

 largest specimen was quite similar to the adult, but the smallest 

 were somewhat different. Instead of the blunt lobes at the margin 

 of the carapace in the adult form, there were 10 pointed teeth, 

 alternately larger and smaller. The length of the carapace also was 

 greater than the breadth, while the reverse is the case in the fully 

 developed crab. In these and other points these small specimens 

 resembled strongly the Circular Crab Atelecyclus heterodon, which is 

 not uncommon off our coasts. I have, however, no doubt that 

 they were really the young of the edible crab, as some of the 

 specimens showed an intermediate condition, in which the pointed 

 teeth were in process of transformation into the blunt square lobes 

 of this species, and no larger specimens of Atelecyclus^ eve -pvesGnt. 

 Moreover, Prof. S. I. Smith, in America, has shown that the young 

 of a species of Cancer on the American coast has pointed teeth in 

 its earliest stage. 



The Circular Crab, Atelecyclus, has always hitherto been classified 

 in the family Corystidae, with the Masked Crab Corystes cassive^ 



