188 NEW YORK STATE MUSEUM 
former specimen the eyes are not only circular, at least that on the left 
side which is fully exposed, but this left eye is also distinctly surrounded 
by a thickened border, and as this border in the adult only surrounds the 
visual surface, the inference is suggested by this specimen that the whole 
node was covered by the visual area. The second specimen suggests that 
here the visual surface still occupied the greater portion of the node, leaving 
only a narrow crescent on the inner side of the node unoccupied. 
The shortness of the segments, compared with their width, is a striking 
feature of these nepionic individuals. The preabdominal segments are from 
6-9 times as wide as long, while in the ephebic stage they are but 4 times 
as wide as long with the exception of the first tergite which retains the 
nepionic dimensions. The first tergite in the first nepionic stage, shows 
no difference in length from the others, while in the next stage [pl. 21, fig. 8], 
it is well distinguished. A specimen [pl. 21, fig. 1] with a length of 5.25 mm 
has but 8 segments. One [pl. 21, fig. 2] which measures 8 mm has already 
the full complement of 12. In the latter the shortness of the segments is 
still more striking than in the former and it appears that the insertion of 
the new segments took place rapidly in successive molts at the expense of 
their longitudinal growth. It is impossible in these young specimens to 
discern the boundary between the pre- and postabdomen. 
The swimming legs are relatively longer and wider in the larval forms, 
as a comparison of figures, plate 21, figures 1 and 2; plate 21, figure 5, 
with plate 21, figure 11 will readily show. In the ephebic specimen the 
swimming leg when reflexed hardly reached beyond the third segment; 
in the first nepionic specimen it extends to the posterior margin of the 
fourth; in the second even to that of the fifth. The specimen, figure s, also 
furnishes evidence of the greater size of this leg in the neanic or following 
stage. | | 
The telson in the nepionic stage does not materially differ in shape 
and relative size from the mature condition. | 
Neantc growth stage. This stage is represented by a considerable 
number of specimens from which the originals of figures 3-11 have been 
