VI 



PENEIDEA AND CARIDEA LARVAL HISTORY 



161 



the biramous thoracic limbs are completed the abdominal biramous 

 pleopods are added, beginning from in front backwards. Thus 

 the Mysis stage (Fig. 109) is reached, which resembles in all 

 particulars the adult condition of the Schizopoda. The adult 

 Prawn develops from this stage by the loss of some or all of the 

 exopodites on the thoracic pereiopods. 



Some of the Peneid larvae take on very peculiar forms, e.g. 

 the Zoaeae of the Sergestidae, 1 which often develop the most 

 wonderful spines all over the body. 



A 2 



Ki<;. 109. Mysis stage in the development of Penevs, sp. A. 2, 2nd antenna; Ab.fi, tith 

 abdominal appendage ; '/', trlson ; '/'//, the biramous thoracic appendages. (After Clans.! 



The ('aridea have a greatly abbreviated metamorphosis, the 

 larva hatching out at a late Zoaea stage with all three pairs of 

 maxillipedes fully formed and with a fully segmented abdomen. 

 The succeeding thoracic limbs are, added in order from before back- 

 wards, though the sixth pair of pleopods appear precociously as in 

 the Peneidea. The other swimmcrets do not begin to develop 

 until the thoraeic limbs are complete. Some Caridea sho\\ a yel 

 more abbreviated metamorphosis, .^. the fresh \\aier fn/n, ///<// 7c,s- 



VarianS of S. Kurope, which hatches out at the Mysis stage. 



We See, therefore, in the metamorphosis of the M.'erma 

 several apparently primitive features. In the first place, a free 

 swimming Xauplius stage is preserved in certain forms, identical 



1 Chitllctuj'T l!< i>orls, xxiv., 1881. 

 VOL. IV M 



