of the Fishery Board for Scotland. 



83 



The little hairs on the propodite and dactylopodite are probably sensory. 

 Fig. 64, ib. t gives a dorsal view of the telson. 



Variation of the Megalops. 



A typical megalops may be described as follows. It walks about by 

 means of the pereiopods, which are now of the adult form, and it swims 

 by means of its large pleopods. The exopodites of the thoracic appen- 

 dages are present, but in varied structure. They may be setose, or 

 much reduced, and without seta?. The antenna? now project as far in 

 front as the chehe can reach, and are used, as in the adult, as feelers. The 

 rostrum is bifurcate at the tip. The eyes, like those of the zoea, are 

 very large. 



The megalops varies in several ways — the following were specially 

 noted : — 



(1) It as often as not has one or more of the dorsal abdominal 

 hooks of the zoea persisting. 



(2) It may have the median spine on the hind border of the telson — a 

 zoea character. 



(3) The exopodites may vary very much. Some or all of them may 

 be setose, or they may be reduced to little processes, as in the first young 

 stage. The exopodite of the first pereiopod does not usually have any 

 seta?. 



The following Table gives an analysis of 12 megalopa with respect to 

 three characters. The sign + signifies the presence, and - the absence, 

 of the character ; if no sign is entered the character had not been noted. 





Dorsal Hooks 

 on 



Abdomen. 



Median 

 Spine on 

 Telson. 



Exopodites — 

 some 

 Setose. 



Exopodites 

 reduced to 

 small pro- 

 cesses. 



4 Megalopa, 



+ 





+ 





1 Megalops, 



+ 







+ 



5 Megalopa, 







+ 





1 Megalops, 







+ 





1 Megalops, 





+ 







Forms Resulting from the Casting of III. and "IV."Zoe,e. 



Particulars were kept of various casts of the III. zoea and of the 

 " IV." stage. The resulting forms were observed, and are entered in the 

 following Table : — 



[Table. 



