STOiMATOPODA. 299 



pairs of swimming limbs whicli follow (Fig. 141, /-!') are biramose, 

 and provided at their ends with setae ; these appendages correspond 

 to the five pairs of maxillipedes found later, while the next three 

 limbless segments {6, 7, S) carry at a later stage the biramose 

 ambulatory limbs. In the stage now under consideration, all the 

 thoracic segments are quite distinct, the five anterior ones being 

 provided with limbs, while the abdomen is still unsegmented. In 

 the following stages, the abdominal segments appear in regular 

 order, as also do the pleopoda belonging to them, w^hile still 

 no trace of limb-rudiments can be seen on the last three thoracic 

 segments. It results from this, that, in the Stomatopodan meta- 

 morphosis, the primitive order of development of the segments 

 (from before backward) is retained, whereas this order is broken 

 through in the formation of the limbs by the belated appearance 

 of limb-rudiments on the three posterior thoracic segments. 



In the next stage (3 mm. long. Fig. 141 A), the first abdominal 

 segment is marked off, and the rudiment of the first pair of pleopoda, 

 still devoid of setae, are already to be seen on it (a\). In the first 

 antenna, the rudiment of an accessory flagellum can be recognised 

 as a short conical process. The five pairs of swimming limbs are 

 also modified. In the second swimming limb particularl}', the 

 endopodite has enlarged as the rudiment of the future raptorial claw. 



In the next stages (Fig. 141 B and C), the dine rent abdominal 

 segments and their limbs continue to appear in regular order. The 

 anterior pair of pleopoda are already developed as biramose lamellate 

 appendages furnished with setae, while those of the posterior 

 segments are more rudimentary in shape (a^-a^). Even the sixth 

 pair of pleopoda («^), which later attains great development as 

 lateral limbs of the caudal fin, is no exception in this respect, but 

 develops last and in a shape exactly resembling the other pleopoda. 



^Meantime, the limbs of the anterior portion of the body, especially 

 those of the maxillary region, undergo important alteration. In the 

 anterior antenna (Fig. 141 D, a), we can distinguish a three-jointed 

 protopodite, a short exopodite beset with olfactory setae, and a longer 

 inner branch (the rudiment of the accessory flagellum appearing at a 

 later stage). The second antenna, besides a fan-like plate which has 

 developed on its extremity, shows the bud-like rudiment of a 

 flagellum. AVhereas the mandible is still for a loner time without 

 a palp, short rudiments of palps have already appeared on the two 

 maxillae. The two anterior maxillipedes (Fig. 141 .B, C, D, I, II) 

 change in the direction of their final shape ; the exopodite which 



