BRACHYURA. 



291 



the dorsal shield and sloping upwards and backwards, and a pair 

 of lateral spines at the posterior lower angles of the shield which 

 slope outwards. At the anterior part of the body, the large, short- 

 stalked lateral eyes rise from broad bases; between them lies the 

 Nauplius eye. The movable abdomen which is used as a rudder 

 for steering, is ventrally flexed, and consists of five free segments, 

 while the sixth still appears to be united in one piece with the 

 .telson. The posterior thoracic region, which later bears the 

 ambulatory limbs, appears in the Zoaea very little developed. It is 

 quite short and rudimentary, is hidden under the dorsal shield and 

 shows either no indications at all of limbs (peraeopoda), or only short 

 truncated rudiments. In the last case it would perhaps be more 

 correct to call the stage at which the larva leaves the egg the 

 Metazoaea. 



The seven anterior pairs of limbs are present in the Zoaea, well 

 developed and functional. The antennae are distinguished by great 

 simplicity of shape. The first antennae are short, unjointed processes, 

 at the ends of which only a few setae develop (in the youngest stage 



of Carcinus 

 maenas only 

 two (Spence 

 Bate)). The second antenna consists 

 of a protopo elite which often grows 

 out into a very long spinous process 

 which is seen less 

 strongly developed in the Anomuran 

 larvae {e.g., Eupagurus). Another 

 spinous process clothed at its end 

 with setae must be regarded as the 

 exopodite (squame, st). The endopodite 

 (rudiment of the future flagellum) is 

 at first altogether wanting, but soon 

 appears in the form of a small prominence which grows out between 

 these two spinous processes. The mandible still consists exclusively 

 of the masticatory blade ; the mandibular palp is altogether wanting. 

 The maxillae already show the structure typical of the Decapoda 

 (Fig. 137 D and E). The protopodite of the first maxilla has two 

 masticatory blades turned inwards and provided with setae, and a 

 two-jointed palp (endopodite). On the second maxilla there are 

 four lobate masticatory processes on the protopodite, two occurring 

 on each joint, an endopodite also divided up into lobes, and an 



Fig. 138.— Zoaea of Thia polita (after 

 Clacs). mf, first maxillipede ; 

 mf", second maxillipede. 



