REPOET ON THE SCHIZOPODA. 163 



remarkable alteration in the armature, most of tlie spines observed in the larval telson 

 at lengtli wholly disappearing, and a few only being left to acquire the peculiar form 

 characteristic of those in the adult animal. 



In the earliest Calyptopis stage described above, the telson (fig. 36) is not yet defined 

 from the last caudal segment. It constitutes a broad spathulate plate, constricted a little 

 posteriorly to the middle, and armed on either side with a strong lateral spine. The end 

 is somewhat expanded and broadly truncate, and its terminal edge fringed with a row 

 of thirteen strong ciliated spines. Of these, the median is very small, the three 

 succeeding ones on either side being somewhat larger and uniform in size. The three 

 outermost spines on either side, occupying the rounded lateral corners, are much stronger 

 than the rest, and the middle one by far the largest, projecting considerably beyond the 

 others. 



In the last Calyptopis stage the' telson (fig. 37) is distinctly defined from the last 

 caudal segment by a well-marked suture, and at its base the uropoda have developed. 

 The form and armature of the telson do not, however, difier materially from those in 

 the preceding stage. 



In the first Furcilia stage the telson (fig. 38) has become somewhat narrower in 

 proportion to its length, and the median of the terminal spines has attained the size of 

 those succeeding it on either side, all forming together an uninterrupted row of seven 

 uniform and comparatively short spines occupying the median part of the terminal edge. 



In the intermediate Furcilia stage the telson (fig. 39) is considerably narrower than 

 in the preceding stages, though still somewhat expanded towards the end, which has 

 assumed a broadly rounded form, the middle part, bearing the seven small spines, being 

 somewhat protruded. Of the three outer spines, the innermost has become remarkably 

 strong, though still shorter than the middle one, and the cdia at its inner edge are 

 coarser and more dentiform. 



In the last FurcUia stage the telson (fig. 40) is almost linear, being scarcely at aU 

 expanded at the end. The middle part of the extremity protrudes considerably, being, 

 however, still truncate at the tip, and bearing the original number of spines (seven), 

 which are very small and densely crowded together. Of the outer spines, the innermost 

 has still more increased in size, being almost as long as the middle one and much 

 thicker, whereas the outermost spine has diminished in size. 



In the first Cyrtopia stage the telson (fig. 41) is very narrow, linear, and the 

 middle part of the extremity juts forth as a conical process, bearing at its narrow 

 truncate tip only three spines, four of the original ones having disappeared. The inner- 

 most of the outer spines, on either side, is now very large and sharpened at the inner, 

 strongly denticulate edge, as also distinctly projecting beyond the others. 



In the last Cyrtopia stage the telson (fig. 42) has nearly assumed its definitive 

 form, being somewhat incrassate at the base and slightly tapering towards the apex. 



