QUESTIONS OF DEVELOPMENT 217 



Anotlier intricate matter is tlie development of Penceus. 

 Fritz MuUer 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 0. F. Miiller gave the name 

 of NaupUus. 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 My sis or Schizopod stages, not 

 to mention the Protozoea of Glaus interposed between the 

 egg and the NaupUus 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 Penceus^ 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 Muller,' to which he adds that ' no 

 observer has rediscovered Miiller's Nauplius.' 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 Penceus ; 

 either of these being demonstrated will prove the con- 

 nection, and establish the splendid hypothesis of Fritz 

 Miiller.' 



6'oZe7^oce?•<x, Lucas, 1850, with its Mediterranean species 

 8olenocera Pliilipjni, Lucas, is by Victor Carus made a 

 synonym of Penceus siphonoceras, Philippi, but it differs 

 from Penceus in having the flagella of the first antennae 

 longer than the carapace, and should therefore be called 

 Solenocera siplionoceras (Philippi), the earlier name Penceus 

 'memhranaceus^ 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, 



