KEEPING DAEK 815 



formed by Latreille from the Greek words icros, equal, and 

 vov!, a foot, but, so far from the legs being all alike or 

 equal as the name would imply, these appendages often 

 have two or three very different developments in a single 

 animal. There is, to be sure, a typical form of limb which 

 prevails very widely, but the exceptional forms are nume- 

 rous and remarkable. With these Latreille was unac- 

 quainted, and therefore naturally gives no clue to them in 

 the name Isopoda, which he himself interprets as signifying 

 ' tous les pieds simples et uniquement propres a la locomo- 

 tion ou a la prehension.' In proportion to their importance 

 in the economy of the world the Isopoda have hitherto 

 attracted little of popular notice. They enjoy still less of 

 popular favour, 'ihey are all of retiring habits, never 

 needlessly coui-ting attention, but in general clinging as 

 closely as possible to whatever shelter or holdfast they 

 have adopted. Amidst enormous disparities of size and 

 strength and shape and temper, this prudent love of ob- 

 scurity, the one feature of the moral character which all of 

 them possess in common, is strong evidence that all of 

 them must have sprung from a common origin. They 

 have never tempted mankind to search for them as food. 

 The services which they doubtless often render as effective 

 scavengers are in some measure counterbalanced by the 

 damage which some of them inflict on submarine structures 

 and the depredations committed by others on the fruits 

 of the garden. Several of the species treat their fellow- 

 inhabitants of the sea with little ceremony, and make up for 

 smallness of size by ferocity of behaviour. It is only to be 

 hoped, as indeed it may be considered certain, that their 

 living victims are immeasurably less sensitive to pain than 

 ourselves. 



Normally the mem bers of this sub-order have an elongate 

 ventrally flattened body, divided into a head of six seg- 

 ments under a carapace, a trunk or peraeon of seven arti- 

 culated segments, and a pleon usually limited to six 

 segments. As in all the Edriophthalma, there is no ap- 

 preciable ocular segment. The carapace is occasionally 

 in coalescence with one or two of the segments of the 



