STAGES IN THE LIFE HISTORY OF CALANUS FINMARCHICUS. 9 
rather long body is armed at the hind end with 4 pairs of lateral hooks, 
2 feelers, 2 end hooks, and 2 pairs of ventral hooks. The maxille and 
maxillipeds are well developed and swimming feet I and II are present 
as bilobed structures. 
This is the last nauplius stage. 
COPEPODID STAGES. 
There are 5 copepodid stages before the animal is fully formed. These 
were recognised by Gran (1902), who gives 6 stages, the last being the 
mature Calanus. All the 5 stages occurred and were taken from ex- 
perimental jars started on March 30th, 1915. Naupln first appeared 
between the 17th and 24th of April, and on May 19th Stage V was taken 
from the jar, having taken certainly less than two months to grow from 
the egg to this stage. 
The species can be recognised from the first copepodid stage by the 2 
long sensory bristles on the penultimate segments of the antennules. The 
rostral processes are distinct even in the first stage, which, according to 
Oberg, is not the case with Pseudocalanus, where they appear only in the 
second stage. 
Stace I (Plate 1, Fig. 6, and Plate 4, Fig. 1). Length of body 0°80 mm. 
Three free thoracic segments and urosome of one segment with an anterior 
constriction. In shape like the adult, but broader in comparison with its 
length. Caudal furca like the adult, but with 3 long bristles and one short 
bristle, besides a short inner bristle each side. The antennules are now 
long hke the adult, and usually held out almost at right angles to the 
body. Colour pale yellow all round the edges of the body, antennules, 
antenne, mandibles, part of maxillule, maxilliped, and caudal furca, the 
tips of all these appendages changing from yellow to red as the extremities 
are reached. Red pigment occurs all along the antennules, the 3 end 
segments being almost completely red, and dark red blotches run from 
the base to about the centre. Traces of red pigment are to be seen in the 
anterior part of the body. Eye dark red. Rostral processes present. 
There are 2 pairs of well-developed swimming feet and one rudimentary 
pair. All the other appendages are well developed. 
Appendage I. ANTENNULE 10 jointed, long, red sensory bristles, one 
on the antepenultimate and one on the penultimate segment. 
Appendage II. Anrenna (Plate 3, Fig. 6). 
Coxopodite very small with one bristle. 
Basipodite, the masticatory bristle has disappeared. 2 bristles present. 
