470 THE VOYAGE OF H.M.S. CHALLENGER. 



Thus we find that important parts vary, change and disappear, yet the animals possess 

 features that clearly demonstrate they belong to one common division. 



Their great nervous system, their manner of fertilisation, their reproduction and, so 

 far as known, their plan of development are similar, and those systemic features 

 which unite the Penseidse and the Sergestidse they possess in common with the aberrant 

 Schizopoda. 



In some genera the ova are carried in a pouch beneath the ventral surface of the 

 pereion, but this is not a universal characteristic of the group, for in his carefully executed 

 Eeport on the Schizopoda, Professor Sars has pointed out ' that, " in the Euphausiidse 

 incubatory lamellse are wanting ; but even here the position of the ova beneath the trunk 

 is precisely the same as in other Schizopoda," and, it may be added, corresponds with 

 the position of the ova in Lucifer as shown by Professor Brooks in his memoir on that 

 genus. 2 



Tribe Schizopoda. 



This name as now applied is much more extended, and bears but little reference to 

 the species for which Latreille originally intended it, most of these having been found 

 to be the early stages of some other forms of more or less known adult Crustacea. The 

 name was consequently withdrawn by its author, and, so far as I am aware, does not 

 appear to have been generally adopted until Claus used it in 1862, and it was not 

 employed in any general classification until 1867, when Sars introduced it into his 

 Histoire Naturelle de Norvege and in his recent Eeport on the Schizopoda of the 

 Challenger Expedition. It will henceforth probably continue to be used as the 

 appellation of this tribe. 



Professor Sars says 3 that, in his opinion, " it is more appropriate at present to assign 

 to this group the rank of a distinct tribe or suborder, there being several well-marked 

 characters distinguishing these Crustacea rather sharply from all other known Decapods," 

 but it appears to me that, with the exception of the variable condition of the pereio- 

 poda, the several genera do not possess a single character that is not beld in common with 

 some genus of the Macrura. 



1. The presence of well-developed basecphyses attached to the pereiopoda, which 

 Sars calls " natatory branches," is common to many genera, especially in immature 

 forms. It was one of the features that induced Milne-Edwards to place the genus 

 Oplophorus among the Penaeidea, with which it possesses no other important character 

 in common. These being ecphyses, or branches of the pereiopoda, they are incapable «f 

 free action to any great extent, independently of the limbs of which they are a part. 

 With the exception of the family Mysidse, in which the pleopoda in many genera are 



1 Zool. Chall. E.\p., part xxxvii. p. 8. 2 Loc. cit., p. 19, 1882. 3 Loc. cit, p. 7. 



