1] 4 MR W. K. BROOKS OK LUCIFER: 
In all three forms the somites, and with the exception of the swimmerets the 
appendages also, develop in serial order from in front backwards. 
The interesting question whether we are to attribute to this typical form of develop¬ 
ment a fifth thoracic somite and appendages must, I think, he left in doubt. A 
comparison of the Sergestid larvse seems to indicate its absence, but wider comparison 
with Penceus and the Schizopods seems to lead to the opposite view. 
Comparison of Penoeus with the Sergestidce. 
In order to render the comparative tables as complete as possible, I have added 
columns showing the corresponding stages of Penceus and Eupliausia. 
Fritz Muller has described a number of stages in the development of a species of 
Penceus (“ Verwandlung der Garneelen,” Arch. f. Naturgeschichte, 1863, pp. 8-23, 
taf. ii.). The series commences with a Nauplius which may belong to the same species, 
although we have no certainty of this. In a second paper (“Ueber die Naupliusbrut 
der Garneelen,’ 7 Zeit. f. Wiss. Zool., xxx., 163-166) he gives, in reply to doubts which 
had been expressed to him by Spence Bate, Alex. Agassiz, Paul Mayer, and 
others, the following reasons for believing in the specific identity of all the forms in 
his series :—1st, the peculiar mode of locomotion; 2nd, the resemblance in colour; 
3rd, the great length of both pairs of antennae; 4th, the character of the mandible ; 
5th, the presence of four pairs of buds in the Nauplius, and four corresponding pairs 
of limbs in the Zoea; 6th, the similarity in the structure of the heart, digestive tract, 
and liver in the Nauplius and the youngest Zoea; 7th, the presence of frontal organs 
in both stages. As all the points except the colour would apply to any Crustacean 
which passes through a Protozoea stage, there is certainly nothing more than a pre¬ 
sumption that the whole of his series represents a single species; but as there is no 
doubt that the Nauplius belongs to Penceus or to some closely-related form, I have 
included it in the table. 
Fr. Muller’s account of the later stages is supplemented by a few additional 
observations of other species by Claus (“ Unter such ungen, 77 &c., pp. 11 and 41, taf. ii. 
and iii.), and I have compiled the columns in the tables from both sources. 
The first Nauplius stage (Table II., column 3) appears to be more simple than that 
of Lucifer, as Muller failed to observe any buds to represent appendages posterior to 
the mandibles. 
The Nauplius stage is followed by a meta -Nauplius stage (Table III., column 2), 
which is distinguished from that of Lucifer by the great size of the blade of the 
mandible, by the presence of frontal organs, and by the shortness of the carapace. 
The next stage is a Protozoea (Table IV., column 5), with a rounded carapace 
without spines or rostrum, four basal rings and six terminal joints in the endopodite 
of the second antenna, a spine on the labrum, two pairs of maxilke, two pairs of 
maxillipeds, and a long hind body which, according to Claus, is divided into six 
