QUESTIONS OF DEVELOPMENT Ze 
Another intricate matter is the development of Pencus. 
Fritz Miiller in 1864 believed himself to have discovered 
the earliest stage. Of the brood of some prawns belong- 
ing to Penceus or some immediately kindred genus, he 
says, ‘they quit the egg with unsegmented oval body, an 
unpaired frontal eye, and three pairs of swimming-feet, of 
which the first are simple, the other two two-branched, 
belonging, therefore, to the larval form so frequent among 
the lower Crustacea, to which O. F. Miiller gave the name 
of Nauplius. No indication of a carapace, of the paired 
eyes, of mouth-organs near the mouth which is over-arched 
by a helmet-shaped hood!’ Between this and the adult 
there are various Zoea and Mysis or Schizopod stages, not 
to mention the Protozoea of Claus interposed between the 
egg and the Nauplius form. Spence Bate alludes to the 
claim made by Professor Brooks in 1882 that, having 
captured and kept in confinement a specimen, he had 
witnessed every moult between the youngest Protozoea 
and the young Pencevs, but against this is set the comment 
of Mr. Walter Faxon in 1883 that Professor Brooks’ 
‘youngest Protozoea is an older stage than the youngest 
stage secured by Fritz Miiller, to which he adds that ‘no 
observer has rediscovered Miiller’s Naaplius.’ Hence 
Spence Bate himself says that ‘two links of importance 
are yet wanting: the one is that which connects the 
earliest Protozoea form with Fritz Miiller’s Nauplius, and 
the other that which connects the Nauplius with Peneus ; 
either of these being demonstrated will prove the con- 
nection, and establish the splendid hypothesis of Fritz 
Miller.’ 
Solenocéra, Lucas, 1850, with its Mediterranean species 
Solenocera Philipyii, Lucas, is by Victor Carus made a 
synonym of Peneus siphonoctras, Philippi, but it differs 
from Penceus in having the flagella of the first antennae 
longer than the carapace, and should therefore be called 
Solenocera siphonoceras (Philippi), the earlier name Penceus 
membranaceus, Milne-Edwards, having been already used 
by Risso for a different species. The flagella in question 
are rather remarkable, since the primary is very slender, 
