A STUDY IN MORPHOLOGY. 105 



the hind body, as shown in the figure, and its hairs are short. As in Lucifer at the 

 same stage, the exopodite is as long as the endopodite. 



The third pair of maxillipeds, and the first, second, third, and fourth pairs of 

 thoracic limbs are represented by buds, as in Lucifer at the same stage. The bud for 

 the third maxilliped (fig. 77, Mp. 3) is bilobed, longer than the others, and it points 

 backwards outside the other buds. The buds for the first three pairs of periopods 

 are bilobed, in contact on the median line, and about equal in size. Those for the 

 fourth pair are much smaller, and are hidden in a ventral view by the buds for the 

 third pair, but they can be seen in side view (as shown at T4 in fig. 78). There is no 

 trace of the fifth pair of pereipods either at this or at any later stage. GLAUS figures 

 buds for the fifth pair in the Zo'ca of Sergestes, and also in the next or Acanthosoma 

 stage of Sergestes ; but the study of the Zoea of Acetes shows even more satisfactorily 

 than is the case in Lucifer that these appendages are entirely absent, and it seems 

 safe to believe that this is the case in Sergestes also until the larva of the latter has 

 been carefully examined with reference to this particular point. 



The abdominal appendages, with the exception of the fifth pair, are entirely absent ; 

 but each abdominal somite has a pair of long ventral spines. The swimmerets are 

 represented by long bilobed buds, which project beyond the fork or notch in the telson. 

 The abdominal ganglia are very much more conspicuous than they are in Lucifer. 



The distribution of pigment is somewhat different from what we find in the Lucifer 

 Zoea, and nearly all the pigment-spots are bright-red. There is a large spot of red and 

 one of reddish-yellow on the eye stalk, a red spot on the labrum, a large red and very 

 dendritic spot on the second antenna, red spots on the dorsal surface of the posterior 

 edge of the third, fourth, and fifth abdominal somites on the median line; red spots 

 on the ventral surface of the first, second, and third at the bases of the spines ; a red 

 and a brown spot at the base of the spine on the fifth ; a brown spot at the base of the 

 spine on the sixth, and a red spot on the base of the swimmeret. The anal spots are 

 large and bright-red. 



On September 20th I found several specimens of the stage which has just been 

 described. Fig. 79 was made from one of them, which was then placed in a glass of 

 water by itself, and the next day it was found to be moulting. In the evening 

 the moult was found to be finished, and the larva was swimming actively. The' 

 drawing given in fig. 84 was made from it without injuring it, and later stages were also 

 drawn from the same specimen. 



The larva, T^-Q inch long, has undergone very great change, and although it is an 

 Acanthosoma, it presents many important differences from both Lucifer and Sergestes. 



The abdomen has lengthened so that the carapace makes less than one-third the 

 total length of the body, and the dorsal and postero-lateral spines have disappeared. 



The abdominal spines stand out from the body, and the swimmerets have become 

 the chief locomotor organs. The spine has disappeared from the labrum ; the two 

 pairs of antennae have changed from the larval to the adult form ; the endopodite of the 

 fourth pereiopod, and the first three pairs of pleopods are represented by long buds. 



MDCCCLXXXII. p 



