146 DEVELOPMENT OF PALINURUS VULGARIS. 



(2) The abdomen is sharply marked off from the thorax^ being 

 much narrower at its base than the latter. 



(3) The ai'ticulation of the thorax with the abdomen is on the 

 same level with the origin of the last pair of thoracic limbs. 



Thus Richters shows that the forms which Milne Edwards 

 distinguished as Phyllosomes ordinaires are the larvae of Palinurus, 

 or genera belonging to the Palinurus division of the Loricata. 



But here we come upon a point which requires elucidation. 

 R.ichters states that the first maxilliped is completely wanting in the 

 youngest larvee of the Palinurus series ; he points out that Dohrn 

 himself describes a reduction of the first maxilliped as having taken 

 place in the embryo almost ready to hatch, and then says that this 

 last stump alsOj without doubt, disappears, since in the young'est 

 Palinurus Phyllosomes which he examined no trace of this appendage 

 was to be discovered. 



The last publication I have to refer to is Spence Bate's Report on 

 the Decapoda macrura collected by the " Challenger." That author 

 says concerning the larvae of Palinurus, that it has been found 

 impossible to keep them alive in aquaria any time after hatching, 

 and that although, no doubt, there are large numbers of these larvee 

 in the sea off our south-west coast, only solitary specimens of the 

 PhyJlosoma form have been occasionally taken. Spence Bate does 

 not figure the hatched larva of our common Palinurus, the true 

 Phyllosoma, but gives instead a figure of the nearly ripe embryo 

 taken from the egg, and this is by no means perfectly similar to the 

 free larva. With regard to the question of the first maxilliped 

 Spence Bates' descriptions throw no light upon it, as he does not go 

 into the details of the oral appendages in his specimens. He was 

 not apparently acquainted with Richters' paper, for he attributes to 

 Palinurus, a specimen of Phyllosoma having the characteristics 

 of those larv£e which Richters has shown to belong in all pro- 

 bability to Ibacus or Parihacus, or, at all events, to develop into 

 forms with short, flat antennee. 



We find then, from the above survey of the literature that 

 although it is clear that Palinurus vulgaris is developed from a 

 Phyllosoma, no single figure or detailed description of. any larval 

 stage, known certainly to belong to this species, has been published 

 except those of Couch, which are unsatisfactory. Claus has 

 published figures of Phyllosomes taken at Messina, the smallest of 

 which Dohrn proved afterwards to be identical with the larva of 

 8cyllarus arctus, now called Arctus ursus, which also occurs, though 

 rarely, in the neighbourhood of Plymouth. The newly hatched 

 larva of Palinurus has been obtained in aquaria several times, e.g. 

 by Gerbe at Concarneau, by Dohrn at Messina, and by Alfred Lloyd 



