ANOMURA. 285 



great elongation of the posterior crystalline cones, causing the eye 

 to project somewhat backwards. 



The My sis stage (Fig. 132 JB), which results from the above through 

 a transitionary stage, shows the fifth ambulatory limb as well as 

 the rudiments of the pleopoda (except those of the first abdominal 

 segment). The exopodites on the third maxillipede and on the 

 three anterior ambulatory limbs (mf"'-p rn ) are provided with setae 

 and function as swimming limbs. The endopodites of these limbs, 

 on the contrary, are still quite embryonic in appearance ; they are 

 unjointed and have no setae. The telson, which has now changed 

 into a long rectangular plate, has, at its posterior margin, a small 

 unpaired spine and seven longer spines on each side. The lateral 

 limbs of the caudal fin (a 6 ) are already developed. 



In later stages, the endopodites of the ambulatory limbs become 

 more developed and the rudiments of pincers become evident on the 

 first ambulatory limbs, while the exopodites gradually degenerate. 



The agreement between the metamorphosis of Gebia and that of the Anomnra 

 consists in the form of the paired eyes and telson, in the biramose maxillipedes, 

 and above all in the condition of the third maxillipede, which is first used 

 as a swimming limb in the Mysis stage, while its endopodite is still rudi- 

 mentary. While, in this respect, the larva of Calliaxis agrees with the Zoaea 

 of Gebia, the Zoaeae of Callianassa and Calocaris agree with those of the 

 Caridea, inasmuch as all the three maxillipedes here function as biramose 

 swimming limbs. 



As a contrast to the features which connect the metamorphosis of the 

 Thalassinidea with that of the Anomura and Brachyura, the distinct develop- 

 ment of the Mysis stage in the former group should be pointed out. This stage, 

 which is characteristic of the Macruran metamorphosis, is, as we shall see, 

 suppressed in that of the Anomura and Brachyura. 



The Zoaea of the remarkable deep sea form Calocaris Macandreae is provided, 

 like the other forms, with well developed paired eyes. The degeneration of 

 these organs, which characterises the adult, takes place only after the Mysis 

 stage (G. 0. SARS, No. 149). 



The Calliaxis larva (GLAUS, Nos. 6 and 7) is distinguished by a curious 

 neck-like elongation of the cephalic region, which causes a certain resemblance 

 to Lucifer. Another feature characteristic of this form, which was described 

 by BROOK (No. 107) as Trachclifer, is the lengthening of the telson into two 

 wing-like lobes bearing spines posteriorly. 



G. Anomura. 



The Anomura in their metamorphosis show a somewhat primitive 

 condition, in which, in many respects, they agree with the Brachyura. 

 In most cases the young leaves the egg as a Zoaea (Fig. 133 A), 

 in which, as in the Brachyura and a few Thalassinidea, the 

 two anterior maxillipedes function as the chief locomotory organs. 



