304 DISCOVERY REPORTS 



they are very small, and I have been unable to separate them. Four pairs of pleopods 

 can be traced under the skin. Uropods absent. 



It is evident that the larvae which should have hatched from these eggs would be 

 not more advanced than those of A. stirhynchus. Hale's observation seems to show 

 that there is poecilogeny in this species, the eggs of some individuals hatching at a very 

 much later stage than those of others. This is a point which should be investigated 

 further, since those instances of poecilogeny which have been recorded hitherto 

 {Palaemonetes, Synalpheus) have proved to have been founded upon mistaken identifi- 

 cation of the parents. 



Key to the Axiid-Callianassid larvae 



1. Epipods present on legs 1-4 Group I, 2 



Epipods absent Group II, 10 



2. Dorsal spines on abdomen unpaired ... ••• Group I A, 3 



Some of these spines in pairs ... ... ... Group I B, 6 



Group I A (p. 306) 



3. Somite 2 without dorsal spine ... D. IV 



Somites 2 and 3 without spine ... B.R. II 



Somite 2 with dorsal spine ^ 



4. Spine formula of telson 13, I, 13 D- I 



Spine formula II, I, II D. II 



Spine formula 8, I, 8 5 



5. Abdominal pleura rounded, dorsal spine of somite 2 not large D. Ill 



Pleura pointed behind ; dorsal spine very large B.R.I 



Group I B {p. 312) 



6. Somite 2 without dorsal spine ... 7 



Somite 2 with single dorsal spine 8 



Somite 2 with a pair of dorsal spines ... D. IX 



7. Margin of carapace with close-set spines in front and behind ... D. VIII 



Margin with close-set spines in front only ... B.R. Ill 



8. Pleura of somite 2 pointed D. VI 



Pleura all rounded ... ... ... ... ... ... ... ... ... ... 9 



Margin of carapace with close-set spines in front and behind ... D. VII 



Margin with close-set spines in front only D. V 



Group II 



Telson of "A" type, with four pairs of pleopods Group II A, 11 



Telson of "A" type, with three pairs of pleopods Group II B, 15 



Telson of " C. I " type, with three pairs of pleopods Group II C, 16 



Telsonof "C. 11" type Group II D, 20 



Group II A (p. 318) 



11. Leg 5 with well developed exopod 12 



Leg 5 with exopod vestigial, or none ... ... ... ... ... ... ... 13 



12. Telson with spine formula 1 1 , 1 , 1 1 ... ... ... ... ... ... ... D. X 



Telson with spine formula 8, I, 8 ... ... ... ... ... ... ... D. XI 



13. Leg 5 without exopod, carapace with denticulate dorsal ridge B.R. V 



Leg 5 with vestigial exopod ; carapace without this ridge ... ... ... ... 15 



14. Telson about four times as long as wide ... ... ... ... ... ... ... D. XII 



Telson about 2J times as long as wide B.R. IV 



9- 



10 



