40 



The method of progression of the animal would seem to 

 indicate that it can migrate to no great distance, as it can 

 only crawl rather slowly by means of its walking legs or make 

 rapid but spasmodic darts by the flexure of its large tail. 

 That we cannot draw such conclusions, however, is rendered 

 probable from the experiments with marked crabs and lobsters 

 in Europe and America, and the interesting occurrence of craw- 

 fish apparently on a grand trek has been observed. This 

 was at Stompneus Bay on the Malmesbury coast, and is re- 

 corded by Mr. MacLachlan who, on one occasion, observed 

 the usual indications of the passage of a shoal of fish close 

 inshore moving in the direction of Lambert's Bay. Steps were 

 taken to put out the seine net for their capture, and this was 

 successfully effected. Instead of fish, however, it was found 

 that the take consisted of crawfish. 



Definite movement from one place to another within a 

 limited area therefore does certainly occur and possibly move- 

 ments on a larger scale. The former is probably determined 

 by a variety of causes. It is stated, for instance, that the large 

 male crawfish found from February to April off Mouille Point 

 will remain there sheltered from the prevailing south-east 

 winds till the first strong north-west wind, when they all 

 disappear from the locality and find shelter under the lee of 

 Robben Island. Again, there must be definite movements in 

 connection with the breeding season, when males and females 

 come together, as, at other seasons, the males and females 

 congregate by themselves in entirely different localities, as 

 is seen in the account of the experimental hauls. Thirdly, 

 there is a definite movement on the approach and after the 

 period of the casting of the shell. This movement is said to 

 be in some cases towards rocky ground, where shelter from 

 enemies may be found in the nooks and crevices of the rocks ; in 

 others towaids a sandy shore, where the animals bury them- 

 selves up to the eyes in sand and there they remain 

 until new hard shell is acquired. 



12. Life History of the Crawfish. 



The egg, still attached to the ventral side of the tail of the 

 mother, is hatched in the spring of the year in shallow water. 



From the egg emerges the first larval form already des- 

 cribed, and this rapidly ascends to the surface of the water- 

 remaining there probably without taking food. 



It then, within a few hours, changes into another form 

 (the Phyllosoma) provided with other and entirely different 

 organs of locomotion, adapted for swimming chiefly in a 



