60 W. K. BROOKS AND E. B. WILSON. 



after they leave the egg. After this first moult the stalks of the 

 eyes, (see Figure 5), elongate, the fold at the posterior edge of the 

 carapace is stretched out so that the latter is now about half as 

 long as the whole body; the rounded front disappears, and the con- 

 volutions and wrinkles of the rostrum and spine are no longer seen, 

 although these processes are still rolled up, as shown in the figure. 

 Figure 5 shows them as they appeared in the zoea which was 

 drawn, but the form of the bends is not at all constant. 



The swimming hairs on the first and second maxillipeds, Mp, 

 Mp', are extended, and these appendages, as well as the telson, 

 are now used as locomotor organs. Spines have now made their 

 appearance upon the posterior edges of the third, fourth and fifth 

 abdominal somites, and the rostrum and processes of the carapace 

 are covered with short hairs. 



In from one to two days after hatching the rostrum and pro- 

 cesses become extended, as in Plate VII, Figure 8, and the zoea 

 assumes the familiar form which has been described and figured by 

 many observers. 



The Appendages: 



The first antenna of the newly hatched larva is shown in Plate 

 VI, Figure 2, and that of the fully developed zoea in Plate VII, 

 Figure 3. 



In the first stage it is covered by the delicate embryonic skin, 

 which follows the outline of the appendage very closely, except at 

 the tip where it is produced into two long, broad, flattened, pointed 

 setae, which are fringed with smaller hairs. These structures, 

 which seems to be swimming hairs, are not present in the zoea 

 after the moult, but in the first stage the antenna carries a single 

 stout sensory hair which, as shown in Plate VI, Figure 2, extends 

 into one of the swimming hairs, more than halfway to the tip. After 

 the moult, Plate VII, Figure 3, the appendage ends in a number of 

 long blunt sensory hairs, from the bases of which fine fibres run 

 downwards to a large club-shaped granular mass, which appears 

 to be ganglionic in nature. 



The second antenna is shown before the moult, in Plate VII, 

 Figure 1, and after the moult in Plate VII, Figure 2. It is essen- 

 tially alike in both stages, but before the moult is loosely invested by 

 the embryonic skin, which is loose and much larger than the true 

 appendage. It consists of a swollen basal portion d, which carries 

 a short pointed external branch, and a longer internal branch. 



