288 CRUSTACEA. 



segmented endopodite, still devoid of setae, appears rudimentary and 

 functionless. The same character is shown by the rudiments of the 

 four pairs of ambulatory limbs which follow (p f -p f "), the largest of 

 which are those of the first pair, and show distinct rudiments of 

 pincers. A similar very small rudiment is also carried by the fifth 

 thoracic segment (not visible in the figure). In the abdomen, the 

 separation of the sixth abdominal segment from the telson has taken 

 place ; we still find no rudiments of pleopoda on the second abdominal 

 segment to the fifth, but the rudiments of the sixth pleopod (a 6 ) 

 appear highly developed. The exopodite is specially apparent as a 

 setiparous plate (Fig. 133 D, a), while the endopodite is a small 

 prominence and is not yet separated from the protopodite. The 

 middle plate of the caudal fin, the telson, is long and truncated, 

 while the indentation evident in the earlier stage has disappeared. 

 The antennae and mouth-parts have also developed further. On the 

 first antenna (Fig. 133 B, a') we now find the short rudiments of 

 the two flagella, in the second antenna (a") the endopodite is cut 

 off from the protopodite, and is commencing to break up into joints 

 the mandibular palp (t) has grown out as a short stump. 



The young stage coming from the Metazoaea can be compared 

 with the Megalopa of the Brachyura. It already, in all essentials, 

 resembles the adult, except that the eyes are still comparatively 

 large, that the abdomen and its limbs have not yet undergone the 

 degeneration characteristic of the adult, and that the asymmetrical 

 development of the body is not nearly so marked. The abdomen is 

 not yet spirally twisted, but is symmetrical, consisting of six well- 

 marked segments, on which (except on the first) pleopoda, provided 

 with long swimming setae, are found. In the caudal fin, as well as 

 in the pincers of the first ambulatory limbs, a certain degree of 

 asymmetry is already evident. The scales of the second antennae 

 have been cast off, the two flagella-rudiments on the anterior antenna 

 have increased in size. The young forms following upon this stage, 

 in which the asymmetry is still little marked, were classed together 

 by M. EDWARDS under the name of Glaucothoe. 



The metamorphoses of Spiropagurus and of Galathea agree in all essential 

 points with that of Eupagurus. The Zoaeae of Spiropagurus are distinguished 

 from those of Eupagurus by the form of the telson, which has no posterior 

 incision. The larvae of Galathea, which so closely resemble those of Eupagurus 

 as often to be confounded with them, can be recognised by the presence of small 

 teeth on the two posteriorly directed points of the dorsal shield (cf. several 

 larval forms belonging here and described by SPENCE BATE, No. 100, as 

 Zoontocaris). 



