no 
MR. W. K. BROOKS OK LUCIFER: 
If we assume the correctness of the extremely probable assumption that Dohun’s 
and Claus’s unknown larva is the earliest Protozoea of Acetes , the resemblances 
between it and the corresponding larva of Lucifer (compare fig. 27 with Claus, fig. 2, 
taf. iv.) are much greater than they are at a later stage. The chief differences are the 
presence in Acetes of rudimentary compound eyes; the great length of the carapace; 
the absence of a rostrum and spines ; the great number of joints in the first and second 
antenna, and the difference in the length of these two appendages; the deep notch in 
the telson. The close similarity between the two larvae at this stage will be seen by 
comparing column 1 of Table IV. with column 2. 
After the moult which ends the Zoea series the differences between the Acetes 
larva (fig. 89) and the Lucifer larva (fig. 53) become much greater, although they do 
not obscure the fundamental similarity between the two forms. In each of them the 
carapace makes less than one-third the total length of the body, and it has a rostrum 
and two antero-lateral, but no postero-lateral or dorsal spines. The first antenna has 
lost its swimming hairs, and has developed one flagellum in each form and two in 
Acetes. In both forms a series of long plumose hairs has appeared on the inner edge 
of the shaft of the appendage. In both forms the second antenna has lost its 
locomotor function and assumed the adult form, but it is rudimentary in Lucifer and 
well developed in Acetes. 
The ocellus is present and the eye stalked and movable in both. 
The fifth thoracic somite and its appendages are entirely wanting in both forms. 
The fourth is biramous in Lucifer, and similar to the ones before it, but in Acetes the 
limb proper has disappeared and the appendage is represented only by an exopodite. 
The second and third pairs of maxillipeds, and the first, second, and third pairs of 
pereiopods are essentially alike in structure in both forms, but in Acetes the endo- 
podites are rudimentary, covered by a cuticle, and functionless. The swimmerets are 
present and very similar in the two forms, but the other abdominal appendages are 
absent in Lucifer, while the first, second, and third pairs are developed, but rudimen¬ 
tary in Acetes. The abdominal somites have acquired ventral spines in both forms, but 
these are very small in Lucifer and long and prominent in Acetes. The telson is long 
and narrow in Lucifer and short and wide in Acetes. The relation between the tw 7 o 
forms at this stave of development will be seen by a comparison of columns 1 and 2 of 
Table VI. 
The later history of the two genera can hardly be divided into parallel stages. 
Lucifer keeps all its Schizopod limbs for at least two more moults, and as shown in 
fig. 54, acquires the rudiments of all the abdominal feet at one time, and before the 
fourth pair of thoracic limbs and the exopodites of' the others and of the maxillipeds dis¬ 
appear, while Acetes (fig. 85) loses its exopodites at once, and the maxillipeds, thoracic 
limbs, and antennae become like those of an adult Sergestid some time before the appear¬ 
ance of the five pairs of pleopods ; and these do not appear together, but in two sets. 
It is interesting to note that although the changes w 7 hich the two forms undergo 
