POST-LARVAL STAGES OF JASUS LALANDII. 107 



This stage was also readily found in the sea. A series of eighty-five 

 tow-nettings were taken at more or less regular intervals in Table Bay from 

 January 1913 to May 1914, and numerous specimens were procured at 

 certain times of the year. In all of these (over several thousands in number) 

 no later stage was observed. The explanation o£ this may be that, in casting 

 their cuticle at this stage, they go to the bottom, and this seems to be 

 indicated also by the sudden disappearance of the phyllosomas from the 

 tow-nettings after the 10th February, 1914, previous to which they were 

 numerous. The procuring of a few cast cuticles on the 12th of the same 

 month is also signijficant. These cast cuticles were quite identical in size 

 and general character to the phyllosomas. Some of the tow-nettings had 

 perfect phyllosomas together with cast cuticles, but no trace of the animals 

 which had shed the cuticle. 



Hahits and Behaviour of Phyllosomas of I'l mm. 



On hatching the naupliosoma rapidly ascends to the surface by means of 

 its setose antennae. The head region is uppermost and the antennules 

 project upwards. The plane of the exopodite and endopodite and of the 

 large parachute-like group of swimming setse is mostly horizontal, and this 

 is effected by the exopodite projecting toward the back of the body, one 

 endopodite in a lateral direction. When the larvae reach the surface they 

 can progress in a horizontal direction, and they then seek out the most 

 illuminated part. In a few hours (4-6) the phyllosoma stage is assumed. 

 The legs are very much longer and project laterally, the exopodite upwards, 

 the endopodite downwards and inwards, except in the case of the thirds 

 which projects out straight behind the body. The two pairs of exopodites of 

 the first and second pereiopods are in active movement, and the long 

 plumose setse with which they are provided would appear to be very effective 

 swimming organs. This, however, is not the case and the forward progress 

 of the body is comparatively slow. From a purely mechanical point of 

 view, they seem badly adapted for progression, as they project well over the 

 centre of gravity of the animal', and their characteristic lashing movement 

 (if too energetic) would result in the body turning a somersault — in fact, 

 this occurrence v/as often observed. The preservation of the balance of this 

 unstable body is, however, effected by the long third pair of walking-legs, 

 which project backwards in the direction of the main axis of the body. 

 They seem quite sufficient to counteract the toppling forward of the body 

 referred to, which may therefore not have been so accidental as it seemed. 

 It was observed also that the body could be made to rotate on its long axis 

 by the movement of these legs, as they are directed away from each other 

 posteriorly. Even with these steering organs, however, the activity of the 

 exopodite is not at all proportionate to the progression of the body, and 

 suggests a respiratory instead of, or in addition to, a locomotory function. 



