A HISTORY OF HEREFORDSHIRE Chilton says, ' in the City of Nelson, but has so far not been recorded from any other part of New Zealand except Mount Egmont, whence a single specimen was sent me years ago by the late Mr. Drew.' " Curiously this very species, which to the general mind is more than any other the typical wood- louse, and which in its specific name bears the stamp of its supposed ubiquity, will sometimes bafHe research even in England. It was sought for with some diligence by two observers during the whole month of August in the neighbourhood of York, on the borders of Herefordshire and Shropshire, and at Walton-on-the-Hill in Surrey, without a single specimen being seen in any of those districts. For the whole sub-class of the Entomostraca there appears to be in this county a complete dearth of recorded information. A few species have now been obtained, enough to prove that the waters of Herefordshire are not envenomed against the ordinary crustacean fauna of English ponds. Two species of Cladocera have been found, microscopic forms of this interesting order which derives its name from the branching horns of the second antennae. These organs are in this group used for swimming, while the so- called feet are enclosed in the pellucid valves of the test. Both the species obtained belong to the family of the Chydoridae, in which both branches of the second antennae are three-jointed, whereas in the more familiar Daphni- dae one branch has three joints and the other four. Our first species is Chydorus sphaericus (O. F. Miiller), probably the commonest of all the Cladocera, but a little miracle of agility. Mr. D. J. Scourfield has published some interesting observations on this small species which bring it into line with what was previously known in regard to larger forms. The partheno- genetic females produce abundant broods without marital assistance. But the case is different with the ephippial females. These much rarer individuals devote a portion of their shell to forming a case for the ' winter ' or ' resting' eggs, which are destined to preserve the race through long periods of drought. So far as forming the ephippium and laying the egg is concerned, these mothers are as independent as their parthenogenetic sisters. Also they can throw off the ephippium when moulting. But when by careful isolation of ephippial females all access of the male was precluded, Mr. Scourfield found that the ephippium was again and again formed and again and again thrown off, while the egg still remained with the mother. The inference is there- fore fairly drawn that these winter eggs need fertilisation, and in fact it is in company with ephippial females that the rare males are most likely to be found. Mr. Scourfield concludes his discussion by saying : — I would heartily recommend anyone wishing to know of a piece of work worth doing, and within the power of an earnest amateur, to take up the study of this question of the times and causes of the appearance of males and ' ephippial ' females among the Cladocera ; and further, as a special object of attention in the inquiry, [would wish] to recommend to his notice the very common little water flea, Chydorus sphaericus?'^ Alona quadrangular is (O. F. Miiller), the second species obtained, is even smaller than the preceding, rarely reaching one-thirtieth of an inch in length, with a much smaller breadth. Among the Copepoda, or oar-footed entomostracans, the family Cyclopi- " Trans. New Zealand Inst, xxxviii, 64 (1905). '" The Annual of Microscopy, Oct. 1898, p. 64. "" Ibid. 6j. 120
