136 



Part III. — Twenty-second Annual Report 



A number of labelled crabs which were received after the publication 

 of the previous paper are recorded in Table VII. One of these crabs (the 

 last in the Table), which is a male measuring 6^ inches across, is especially 

 interesting. It was recaptured after an interval of three years very near 

 the place where it was set free. When liberated it was a soft crab, and 

 it had not cast its shell during its period of freedom. The abstention of 

 the large crabs from casting has been exemplified by a number of 

 instances, but the time of abstention has only been determined by 

 secondary proofs. For example, a crab is captured with an oyster attached 

 to its back. Since the age of the oyster may be more or less accurately 

 judged from its size, a part of the period that has elapsed since the 

 ecdysis has been determined. Thus Buckland recorded two crabs which 

 had on their backs three-year- old oysters : they could not have cast for 

 three years. Another, now in the Ipswich Museum, is said to have a 

 four-year-old oyster on its back. 



The present case gives a definite abstention for three years at the time 

 of capture. At the beginning of 1903 it had not cast, and would not 

 probably cast then till the summer. This would make the abstention 

 from casting four years. There, of course, comes a stage when the crab 

 ceases altogether from casting. 



Meek gives* a list of the labelled crabs set free on the coast of 

 Northumberland and which have been recaptured at various times during 

 1902 and 1903. One of these is of special interest. Set free in October 

 it was captured in the following July at Portlethen (near Aberdeen), a 

 point about 80 miles to the north of the place of liberation. 



The Changes in the Carapace of Cancer pagurus. 



Cunningham in his paper on the early post-larval stages of this 

 Crustacean drew attention to the great difference between the early and 

 the adult form of the carapace. In the adult the carapace is broadly oval 

 in shape, and is crenate at the edge. In the very young crab the edge is 

 toothed. In his opinion the general resemblance of the carapace, in this 

 stage, to that of Atelecyclus heterodon, along with certain other points of 

 similarity, indicated a closer affinity between the two species than had 

 previously been recognised. 



I have had the opportunity of examining one of the series of casts 

 belonging to Mr. Waddington (A, Table VI.). They are, with the excep- 

 tion of the first, shown in natural size in figs. 71-81. The changes which 

 take place in the shell are well seen. In fig. 103 an enlarged drawing 

 of the second of the series is shown ; it measures 4*75 mm. across 

 the broadest part of the back. The carapace has five main lateral 

 teeth, of which the first forms the hind edge of the orbit, while the 

 fourth projects laterally farther than the others. The main teeth are all 

 serrated ; between each two a secondary tooth is found. The rostrum 

 consists of three dentate lobes. The edge of the orbit is serrated ; and on 

 the surface of the carapace and on the limbs there are numerous small 

 teeth. 



In the next stage (fig. 102) — 5*75 mm. in greatest breadth — a very 

 considerable advance on the preceding is noticed. The secondary teeth 

 have increased in proportional size, and with the main teeth are now more 

 lobate or rounded. All of the lateral edge and the margin of the orbit 

 is minutely dentate. On the rostrum the three lobes show merely a 

 minutely notched anterior edge — the serrations being rounded, not tooth- 

 like. The chela is furnished with tooth-like tubercles. 



*"Meek, "The Migrations of Crabs." — Northumberland Sea-Fisheries Committee. Report 

 on the Scientific Investigations for the year 1903. Newcastle-on-Tyne, 1904. 



