30 



the water. These are the only active locomotary appendages 

 at this stage, all the others being more or less folded up under 

 the body. The first two pairs of walking legs are branched, 

 but the outer branch, though segmented, is not yet provided 

 with swimming setae as in the next stage, and the inner branch 

 is folded in itself. The last two pairs of walking legs are 

 awanting. 



When this larva moults it undergoes considerable change. 

 The swimming setae of the antennae are thrown ol^ and these 

 appendages no longer perform the function of locomotion. 

 This is now performed by the outer branch of the first two 

 walking legs. Hitherto this has been a simple rounded organ, 

 but on the shedding of the cuticle it expands into a feather- 

 like structure with lateral projections or setae, which again 

 are provided with smaller setae, so that the whole forms an 

 effective instrument for swimming purposes as the three walk- 

 ing legs, instead of being folded up under the body as in the 

 previous stage, are now widely expanded. A change has 

 taken place, too, in the body, which is no longer opaque, but 

 is glassy and transparent. This stage (the typical " phyllo- 

 soma ") has been procured in the aquarium at St. James and 

 also by means of fine nets in Table Bay. 



A single specimen has been found at a more advanced stage 

 in which the third pair of walking legs has acquired a swimming 

 outer branch and a fourth leg with the rudiments of the fifth 

 pair appears. 



Amongst other phyllosomas found in townettings a larger 

 form (33 mm. in length) appears to be a still later stage of the 

 crawfish . Fuller results of these investigations will be published 

 with figures at a later date, when more data may be procured 



7. Habits of the Larval Crawfish. 



On hatching, the young crawfish in the first free stage casts 

 off the cuticle of the previous stage. This cuticle may be 

 seen lying alongside or partly protruding from the ruptured 

 egg capsule. The large swimming antennae are at once spread 

 out, and apparently the larvae cling to the surrounding eggs, 

 or are retained in some way in their midst, until shaken off 

 by the vigorous movement of the tail of the parent. 



The larva then rises quickly to the surface by a series of 

 rapid movements in a vertical direction. This is accomplished 

 by the up and down movement of the antennae with their long 

 setae. The exopodite projects towards the dorsal side of the 

 animal, the endopodite being in the same plane but projecting 

 laterally. The large wing-like or rather parachute-like struc- 

 ture formed by the rays is so constructed that, on the downward 



