36 G- 0. Sårs. 



caudal fan. In the present stage, they are, however, rather 

 small, scarcely extending beyond the middle of the telson. 

 They each consist of a thick basal part and 2 terminal 

 plates, the outer of which is the larger, and terminates in 

 a strong spine, inside which a few short setæ are seen to 

 issue. The inner plate is still quite rudimentary, forming 

 an obtusely conical projection without any armature. 



The telson (see fig. 12) has the form of a rather large, 

 oblong quadrangular plate, being about twice as long as it 

 is broad, and on the whole is very unlike that in the adult 

 animal. It is of nearly uniform breadth throughout, and has 

 the extremity obtusely truncated, and armed with a dense 

 row of denticulated spines, 13 in all. Of these spines the 

 7 median are of about equal length, whereas the 3 outer- 

 most on each side, occupying the somewhat rounded lateral 

 corners, are considerably stronger, and gradually increase in 

 size from the 1st to the 3rd, which is the largest. In 

 addition to these, 2 other spines are seen attached to the 

 sides of the telson, opposite each other, and somewhat more 

 ventral. 



As to the internal organs, they exhibit on the whole a 

 similar structure to that found in the 2 preceding stages, 

 and they now appear with great distinctness through the 

 pellucid integuments. 



The larva moves with great agility through the water 

 by rapid strokes of the antennae, partly also by abrupt 

 bends of the metasome. It seems chiefly to feed upon 

 small Diatomeæ, the remains of which could be distinguished 

 by a microscopical examination of the contents of the intestine. 



By a single exuviation this stage is transformed to the 

 1st FurciMa-st&ge, the most conspicuous difference between 



