84 ME. W. K. BROOKS ON LUCIFER: 



equal in length, although even at this stage the endopodite is a little the longest. 

 Each ramus ends with a pair of very short hairs. 



The appendage now changes with each moult, and in the third Schizopod stage 

 (fig. 54) the exopodite has become a scale (fig. 57, ex) while the endopodite (en) has 

 elongated, and now forms a seven-jointed flagellum, about as long as the first 

 antennse or the carapace. The basal joint (fig. 57, b) is thick and swollen, the two 

 proximal joints of the flagellum (2 and 3) are short ; the next (4) long, and the other 

 four about equal in length, and about half as long as the joint (4). 



Through all the Schizopod stages the structure of the labrum (L) is about as it was 

 in the Protozoea and Zoea, and its interior angle is still produced into a short stout 

 sharp spine. 



The mandibles are cutting jaws with no trace of a palpus, and at the first Schizopod 

 stage (fig. 51) the denticles are numerous and of nearly uniform size. In the last 

 Schizopod stage (fig. 58) a second set of denticles has appeared on the outer surface 

 of the blade a short distance from the cutting edge. 



The first maxilla (fig. 52) is very much like that of the Protozoea and Zoea, but the 

 cutting hairs upon the two basal joints (1 and 2) are more numerous, and a small 

 slender plumose hair has appeared near the edge of each joint. The scaphognathite 

 is small and has only two hairs, which are less regularly plumose than before. 



The scaphognathite of the second maxilla (fig. 53, sc) is now rudimentary and has 

 no hairs. The hairs on the inner edge of the appendage are shorter than they were 

 during the Zoea stage, and all of them are plumose and about equal in length. 



The first maxilliped (fig. 50, Mp. 1) has not changed very much, although its joints 

 are nearly absent. The exopodite is about as long as the endopodite, and all the hairs 

 on the appendage are short and plumose. 



The second and third maxillipeds and the four pairs of thoracic appendages are well 

 developed, as a series of long biramous or Schizopod feet, which are essentially alike in 

 form and structure, and, with the telson and swimrnerets, now form the locomotor 

 apparatus of the larva, which no longer swims by jerks but darts through the water 

 with great rapidity, and is able to offer considerable resistance to the suction of a 

 dipping tube. Each swimming foot consists of a two-jointed basal portion or protopo- 

 dite, a long four-jointed endopodite, and a much shorter exopodite. The exopodite is 

 flat, pointed, and its outer or distal half is marked by a series of six pairs of notches, 

 or annulations, close together. The terminal joint carries a pair of long slender 

 unplumose hairs, and a pair of similar hairs springs from each annulation, so that there 

 are fourteen hairs in all on each exopodite, arranged so as to form a large fan -shaped 

 paddle at the tip of the limb. The terminal joint of the endopodite is much shorter 

 than the others, and it carries six long plumose hairs. The first appendage in this 

 series, the second maxilliped (fig. 59, Mp. 2), is somewhat rudimentary: the endopodite 

 is scarcely longer than the exopodite, and its hairs are short. The next or third 



