BRACHYURA. 293 



wanting. Claus, however, has described the presence of a long frontal spine 

 on the Zoaea of Maja. In a larva described by Dohen (No. 121) as Fissocaris, 

 which has a long frontal spine and two pairs of large lateral spines, the dorsal 

 spine is wanting. In other cases the dorsal and lateral spines may be exceed- 

 ingly long, and may end in balloon-shaped swellings. Larvae thus provided 

 with lateral spines projecting backwards were described as Pluteocarialae by 

 Claus (No. 8). A Zoaea form distinguished as Pterocaris is remarkable for 

 the wing -like elevations of the lateral parts of the carapace, and for the 

 transversely-broadened form resulting from this. 



Many of the Zoaeae of the Brachyura are distinguished by the great develop- 

 ment of the spinous process on the second antenna ; e.g., those of Xantho 

 rividosus (Goukret, No. 130) and of Panopeus Sayi (W. Faxon, No. 125), 

 in which this process equals in length the long frontal spine. 



When the youngest Zoaea leaves the egg, it is not altogether free, but 

 appears surrounded by a somewhat loose and detached larval integument 

 (p. 119) ; this has been claimed by Conn as the cuticle of the Protozoaea stage 

 passed through during embryonic life. Only after a moult, which usually 

 takes place early, does the Zoaea become free. A similar condition is found 

 in many other Decapoda (e.g., in all Anoumra and many Macrura). F. Mullei: 

 (No. 16) has pointed out the morphological interest of a study of this larval 

 integument, the form of the tail in this youngest integument in Achaeus, and 

 perhaps also in Maja, recalling that of the shrimp larvae. This larval cuticle 

 Avas utilised later by Paul Mayer (No. 137) in an attempt to derive the different 

 forms of telson and for phylogenetic purposes. More recently, further investi- 

 gations with regard to it have been made by W. Faxon (No. 125) and Conn 

 (Nos. 114 and 115). The spinous processes of the dorsal shield are always 

 wanting in the larval integument, but are often present as rudiments beneath 

 the cuticle, withdrawn in a telescopic manner. While, in the group of the 

 Grapsoidea (Sesarma), the larval integument, apart from the spinous processes, 

 is a fairly true cast of the Zoaea which proceeds from it, in most other 

 Brachyura it shows no inconsiderable deviations from that form. The antennae, 

 hilly, appear in the larval integument in a higher degree of development. 

 The first antenna consists of a protopodite and two terminal blanches provided 

 with setae, one of which is of considerable length. The second antenna is 

 specially remarkable for the presence of laige processes provided with setae 

 on the exdpodite. In the posterior region of the body, the caudal fork is usually 

 characterised by possessing seven feathered setae on each side. The number 

 :i seems to be typical in the setae of the telson throughout the Decapoda, 

 and renders the study of the hatched Zoaea before the casting of the larval 

 integument a valuable aid in tracing back the shape of the telson, which often 

 varies in a later stage, to the fundamental form already described (Tauj. Mayer). 



The series of ontogenetic stages which follow after the Zoaea 

 have usually received the same name, but have been more suitably 

 < -a! l<'il Metazoaeae by Claus (No. 7). They do not, in general shape 

 (';/*. the somewhat younger stage, Fig. 138), entirely resemble the 

 Zoaea, but are distinguished by the greater development of the 

 limb-rudiments. In the first antenna (Fig. 137 A) there is now an 

 unjointed protopodite showing the rudiment of the auditory organ 

 as a vesicular swelling, and two rudiments of flacella, the inner still 



