469 



Metamorphosis and Life-history of Glnathia maxillaris. 



i5y 



Oeoffrey Smith, 



New College", Oxford. 



With piate 18. 



Tlie Gnatbiidae or Auceidae liave been tbe sui)ject of an ex- 

 celleut meuioir by Hesse (1), wbo discovered tbe relationsbip of tbe 

 bxrval form. Prauiza, to tbe adult, wbile Dohkn (2) added a valuable 

 raorpbological essay. Sars (3) bas also made some observations on 

 tbe Norwegian species. Wbile investigating tbe secondary sexual 

 cbaracters of certain Crustacea at Naples I becarae Struck witb the 

 extraordiiiary variability in size of tbe single species of Gnatlna 

 iubabitiug tbe Bay of Naples, and to tbis furtber reference will be 

 made wben we come to consider tbe life-bistory: but first, siuee I 

 bave on numerous occasions suecessfully observed tbe final meta- 

 morpbosis of tbis Crustacean, and some doubt still exists as to certain 

 points, it seems wortb wbile to give as complete au account as possible 

 of tbese remarkable cbanges. 



1. Final Metamorphosis of Praniza into Adult. 



Tbe Praniza larva lives ecto-parasiticaliy on various kinds of 

 fish ; its mid-gut becomes greatly distended witb tbe blood of its host 

 and in consequence the tbree last thoracic Segments (not couuting 

 the rudimentary sixtb) become fused and lose all trace of segmen- 

 tation (PI. 18 fig. 1). Tbe moutb-parts, consisting of maudibles, 

 two pairs of maxillae and two pairs of maxillipeds. are adapted to 

 Piercing and clinging to tbe flcsb of tbe host (fig. 2Ì. Up to a late 

 stage tbe Pranizae are sexually iudistiuguislia))le, apart from tbe 

 ditference of tbe sexual elements tbemselves. 



Metamorphosis into tbe male. Tbe adult male (fig. 3, with 

 its Square head and powerful mandil)les, in tbe degeneration ofthe 



