164 



KNOWLEDGE. 



[July 2, 1900. 



in cither instance is it known upon what objects they 

 operate. To serve their private ends they very likely 

 use the moral or intellectual quality nowadays described 

 as slimness, in suitable accordance with their slenderness 

 of form. Of the equally curious family Gnathiidse, com- 

 pleting the tribe Flabellifera, discussion must be held 

 in reserve. 



Of the Valvifera a specimen has been already figured 

 (Knowledge, Vol. XXI., p. 3). The name of this tribe has 

 reference to the uropods, which fold like valves, or rather 

 meet like a pair of folding-doors, so as to enclose and 

 shelter when necessary the natatory respiratory pleopods. 

 In regard to Anthura it was mentioned that the uropods 

 folded over the telson. Here they fold under it, and by 

 a curious modification this which is the last pair of 

 appendages looks as if it might be the first, because it 

 covers the five pairs of pleopods which in order of attach- 

 ment all precede it. In the family Idoteidfe the legs 

 show tolerable unifoi-mity, but in the co-tribal family 

 AstacillidtC there is often strong diversity between the 

 set consisting of the first four pairs and that consisting 

 of the last three. The hinder group are of normal 

 pattern, adapted for clinging to seaweed or other suitable 

 marine objects. The anterior set are slender and feeble 

 and fringed with setse. These four pairs ai'e close 

 together and close to the mouth, and are no doubt much 

 concerned with the food-supply. But the first seizure of 



young ones have repeatedly been found clinging, like 

 wind-waving articles on a laundress's clothes-line. One 

 observer has recorded that " the parent neither testified 

 impatience of their presence nor seemed to suffer any 



Jnf/ii'liira floiipafa^ Xonii;iii. 



prey is said to be accomplished by the powerful lower 

 autenuse. In this case, however, the prey will not con- 

 sist of sharks and dog-fishes, but of minute organisms, 

 such as can be passed on from the antennje to the setose 

 legs find held within their network of hairs or sctte at 

 the disposal of the selective jaws. The long antennse in 

 this family have another function beside that of grasping 

 prey. They form a soi-t of perch to which rows of 



Asiavilla damnoniensis^ Stebbing. 



inconvenience under the burden." The same observer, 

 however, believed that with rapidly advancing growth 

 the young " certainly proved an annoyance which was 

 ultimately fatal." That the mother either invites or 

 has no wish to hinder the presence of her little ones in 

 so peculiai' a situation is evident, for otherwise her long 

 antennje would be at once and instinctively passed be- 

 tween the fringing hairs of the front limbs, to be cleai'ed, 

 as in this way they habitually are, of encumbering 

 objects. But the habits of Crustacea quite forbid the 

 supposition that the mother would permit the rising 

 generation after birth to cause her serious inconvenience, 

 when a fimple bending of her antennse would enable her 

 to brush them off or eat them up. 



Omitting from this sketch the strange parasitic tribe 

 of Epicarida or Bopyrida, to which some allusion has 

 been previously made (Knowledge, Vol. XXII.. p. 138), 

 we must give a concluding paragraph to the Asellota. In 

 these the uropods are terminal instead of lateral, and 

 in the female the first pleopods are usually consolidated 

 into an opercular plate, thus fulfilling an office per- 

 formed by the uropods in the Valvifera. Also in the 

 female of the Asellota the second pair of pleopods is 

 always wanting. This tribe includes the extremely 

 common fresh-water species, Aselliis aquatlcus (Linn.), 

 in which the feet are of a fairly uniform pattern. On 

 the other hand, it also includes some of the rarest and 

 strangest species of the whole order Isopoda, and some 

 to which that name by its meaning is the least ap- 

 plicable, inasmuch as the feet show very exaggerated 



