90 
MR. W. K. BROOKS OK LUCIFER: 
This sexual difference lias been pointed out by Dohrn (Zeit. Zool., xxi., 1871, p. 358), 
but it seems to have escaped the notice of all other observers. 
In the young and in the mature female (fig. 72) the rounded tip projects beyond the 
tooth (a), but as the male approaches maturity the outer edge lengthens, thus pushing 
the tooth out, as shown in fig. 73, until the end of the appendage becomes square 
instead of rounded. It is extremely interesting to notice that in Lucifer, as in so 
many other animals, the adult female is infantile in all the secondary points of 
difference from the male. 
General view of the metamorphosis of Lucifer. 
A review of the facts which have been described in this section indicates that some 
ol the changes are much more significant than others, since the number of moults is 
much greater than the number of distinct larval type. 
The meta -Nauplius is obviously a Nauplius with the rudiments of structures which 
are to appear after the moult, and it must therefore be regarded as a Nauplius 
prepared for the change into a Protozoea, rather than a distinct stage of development. 
There is no such break between the first Protozoea and the last Zoea as there 
is between the first Protozoea and the Nauplius. The rudimentary pereiopods and 
swimmerets of the so-called Zoea are nothing but a preparation for the next stage of 
development, and the supposed necessity for finding a stage which can be directly 
compared with the Zoea of the higher Decapods does not justify us in making two 
larval types out of the unbroken series of Protozoea and Zoea forms. 
It is obvious that the three Schizopod stages are modifications of a single larval 
type, and the presence of rudimentary pleopods in the second and third stages must 
be regarded as a preparation for the next stage of development. 
There is no abrupt break between the so-called Mastigopus and the young Lucifer 
when it is a little older and the neck has appeared. 
On the other hand, there is a real break between the Nauplius and the Protozoea, 
and the change from one to the other is accompanied by profound structural changes. 
This is the case also with the transition from the Zoea to the Schizopod stage ; and 
with that from the Schizopod stage to the young Lucifer stage. The same thing is 
true to a lesser degree of the change from the immature Lucifer to the adult male. 
The metamorphosis may then be divided into the following well-marked stages, each 
of which except the last, and in all probability the last also, persists through more 
than one moult:— 
1 . A Nauplius stage. 
2 . A Protozoea stage, 
3. A Schizopod stage. 
4. An immature Lucifer stage, which persists in the female. 
5. An adult male stage. 
