1888.] Messrs Brook and Hoyle on British Euphausiidoe. 417 
We were not fortunate enough to secure any eggs which were in a 
more advanced state of development than that just described, and 
the reference of these to the family Euphausiidae rests upon an 
observation made by Dr Murray. He found in one of his gatherings 
certain eggs in which the development seemed pretty far advanced, 
and by skilful manipulation he succeeded in rupturing the external 
envelope, and thus liberating a nauplius, which he recognised as 
corresponding exactly with that about to be described in the present 
paper. 
2. The larger Eggs measured 0'75 mm. in diameter, the blasto- 
sphere measuring 0‘3 mm. Beyond this no differences worthy of 
special mention were noticed between the two kinds of eggs. 
II. The Nauplius. 
The Nauplius has an egg-shaped body, measuring 0*6 mm. and 
0*4 mm. in its greater and lesser diameters respectively. The 
greater portion of the body is filled with a mass of highly refracting 
granules. Xo mouth was detected in it, but a minute triangular red 
eye was distinctly visible close to the anterior extremity. 
The three pairs of appendages characteristic of the Nauplius were 
present. The first pair were unbranched, and about two-thirds the 
length of the body ; the extremity was blunt, and armed with from 
three to six long hairs. The second pair were biramous, and the 
extremity of each branch was similarly armed with a tuft of hairs. 
When the animal was at rest both the first and second pairs of 
appendages were directed forwards, and then their extremities were 
about on a level. The third pair of limbs were placed just anterior 
to the middle of the body, and were much shorter than either of the 
other two, not exceeding one-third of the body in length. Like the 
second pair, they were biramous, each branch bearing a tuft of hairs. 
In the position of rest they projected at right angles from the sides 
of the body. 
The Nauplius which has just been described bears so close a 
resemblance to that figured by Metschnikoff,* that there is no 
reasonable doubt that it belongs to one of the Euphausiidse, but 
whether it belongs to the larger or smaller egg, whether it belongs 
to Nyctiplianes or Boreophausia, or whether, as is most likely, an 
* Zeitschr. f. wiss. Zool., Bd. xxi. pi. xxxiv. fig. 2, 1871. 
