256 A HISTORY OF EECENT CRUSTACEA 



CHAPTER XVIII 



SUB-ORDER III. — SCHIZOPODA 



The mandibles have generally an elongate 'palp.' The 

 second and third maxillipeds are similar in general struc- 

 ture and function to the series of trunk-legs, the whole 

 seven pairs of appendages, and in general the first maxilli- 

 peds also, being provided with well-developed exopods or 

 swimming-branches. There are no chelipeds. The ova 

 are carried by the female beneath the trunk, either with 

 or without the protection of marsupial plates, and gene- 

 rally one or two of the larval stages are passed through 

 before the hatching of the young animal. The males are 

 generally distinguished by a special appendage on the first 

 antennee and by larger pleopods. 



The name Schizopoda, ' cleft-footed,' refers to the 

 double character borne by so many of the appendages, in 

 which the main stem or endopod is more or less ambulatory 

 and the exopod is adapted for swimming. The affinity 

 which the Schizopoda show to some of the Macrura, such as 

 the Pasiphaeidae, and the definite opinion of Mr. Spence 

 Bate that they ought to be included as an aberrant group 

 among the Macrura dendrobranchiata, have been already 

 noticed. Whether they should stand just inside or just 

 outside the sub-order of the Macrura, is a nice point of 

 classification for the learned to decide. 



Pour families are at present included in the Schizopoda, 

 the Lophogastridse, Eucopiidae, Euphausiidse, and My- 

 sidse. But on the one hand a suggestion has been made 

 that two forms hitherto assigned to the Mysidae may re- 

 quire the institution of a separate family, and on the other 

 hand Mr. G. M. Thomson, the well-known naturalist of 



