A STUDY IN MORPHOLOGY. 
77 
In the case of Lucifer the actual increase in size is not very great, but the carapace 
becomes folded out over the body, and the thick posterior portion of the body of the 
Nauplius becomes pulled out into the long free movable hind body of the Protozoea, so 
that the length is more than doubled, while the vertical thickness of the body is 
correspondingly reduced. The shape of the larva when seen from one side will 
be understood by a reference to Plate 4, fig. 35, for although this figure was drawn 
from an older larva, it correctly represents a side view of fig. 27 in all essentials. 
The most marked differences between the meta -Nauplius of Lucifer and the Protozoea 
are due to the development of the carapace and the hind body. The carapace 
(fig. 27) is horse-shoe shaped, with smooth lateral and posterior edges, and it forms 
about one-half of the total length of the body. On the median line of the anterior 
edge it is drawn out into a long rostrum (P), at the base of which are the cerebral 
ganglia (go) and the ocellus ( Oc ). On the median line of the posterior edge of 
the dorsal surface there is a shorter dorsal spine (ds), and at the outer angles of 
the posterior edge a pair of lateral spines (Is), which are a little longer than the dorsal 
one. The side view (fig. 35) shows that the sides of the carapace have folded 
down on to the sides of the body, and all the appendages, except the antennee, 
are almost completely covered by it. The appendages are so nearly alike in this and 
the next stage that it will be most convenient to describe them together. 
The stomach (s) is now divided into a pair of anterior or cephalic, and a pair 
of posterior or hepatic lobes, and between the cephalic lobes a number of muscular 
fibres run upwards and forwards from the oesophagus to be attached (at to) to the 
carapace. The intestine is small and straight (i), but it is not of uniform character, 
and is divided into a series of small enlargements separated from each other by 
cod strict ed portions. 
The last of these enlargements is much more constant than the others, and its walls 
are attached to the integument of the abdomen by a number of small muscles. 
It exhibits regular pulsations, which seem to draw water into and out of the anus 
(a), which is on the ventral surface of the telson. 
The heart (h) is compact, short, situated near the posterior edge of the carapace, 
and it gives rise to a single median and two lateral anterior arteries. 
The hind body is about as long as the carapace, and it is divided into four somites 
and a long unsegmented region (abd). The study of the appendages shows that the 
four somites are those which carry the third pair of maxillipeds (Mp. 3), and the first, 
second, and third thoracic somites (T 1, T 2, and T 3). There are no traces of appendages 
on any of them. The end of the unsegmented region of the hind body forms a well- 
marked flattened telson (T), which is slightly notched on the median line, and carries 
four pairs of stout spines, and one pair of very small ones. The small ones are nearest 
the median line ; the third pair are the longest and largest, and the fifth pair spring 
from the edges of the telson, some distance from the end. 
