200 Prof. C. Cliilton on the Freshwater Jsopods 



wliicli is iH'!)vest to France. Wlien tlie distribution of tljo 

 Diplopoda of these islands is better known, we may find that 

 such an occuirence has a s])ecial biological significance. 

 , 'I'he wood wliere our s[)eciinens were capiureil i-s situated 

 along the slopes and summit of the low chalk-hills which 

 form part of the Wye Downs, running roughly north and 

 south about a mile from AVye itself, and rising on the south 

 trom tiie iSelbornian tract b;.'low, and on the west from the 

 Ciialk vallev of the Great Stour, to a little over 500 feet above 

 sea-level in some places. In the area of the wood where wo 

 took P. germanicum, some three-rpunters of a mile E.N.l'j. 

 from the town, the altitude is only some 400 feet, or 200 to 

 300 feet above Wyo itself. In this i)ortion of the wood 

 hazel, beech, and coniferous trees are well lepresented, while 

 the ground is often covered witii giass and low-growing 

 plants, among which there is a considerable quantity of fallen 

 leaves and other plant debris in autumn. It is among the 

 fallen leaves in this situation that we have taken Folyzonium. 

 As Mr. Diiffield pointed out to me on one of our visits to this 

 hunting-ground, there is quite a striking .superficial resem- 

 blance between this new millipeJe with its yellow to 

 brownish colouring and the fallen bud-cases of the beech to 

 be found at Junij)er Wood in the vegetable debris in which, 

 as already stated, the animal itself occurs. 



Keferences. 



(i) Latzf.l, KonKRT. 'Die Myriopoden der osterreicbiscli-uugarisclien 



Monarcliie," ii. (1884). 

 (i) PococK, K. I. Article "Millipede" iu Encyc. Brit. 11th edit. 1911, 



xviii. pp. 468-475 et seq. 



(3) SiN('LAiR, F. G. "Mvriapods" iu 'The Cambridge Natural History,' 



I'JIO, vol. V. v)p. 27-80. 



(4) Veiuioefk, K. Nv. " Ueber Diplopoden aus Bosnien, Ilcrzogowina 



uud Dahuatieu. — Y. Glouieridte & Polyzouiidiie (Scliluss)." 

 Arcliiv I'iir Naturgescbichte, Jahrg. 64, 1898, pp. 101 et seq., 

 pi. vii. 



(5) . ' Die Diplopodeu Deutschlauds,' 1911-14. 



Wye College, Kent, 

 rjLli December, 1919. 



XXVIII. — Note on the Freshwater Isopods known as Asellus 

 aquaticus. By CiiAS. CiiiLTON, M.A., D.Sc, M.B., CM., 

 LL.D., C.M.Z.S., F.L.S., Professor of Biology, Canterbury 

 College, New Zealand. 



The little freshwater Isopods which are common in many 

 streams oE diil'erent parts of Euro])e have hitherto always 

 been known under the name of Aifellns aquaticus, and, 



