476 On the Eiitomosfraca of Lake Bassenthwaite. 



common. Brady says that it rarely occurs in lakes or large 

 sheets of water, but generally in ponds and ditches where 

 there is much vegetation. This species was not very abun- 

 dant in April, and no specimens were taken in June. 



Diaptomus gracilis , Sars. 



Diaptomuif (/raci/is, Brad}', Kev. Brit. Freshw. Cyc. and Cal. p. 29, 

 pi. xi. figs. 7-9, pi. xii. figs. 1-8. 



This species is universally distributed and abundant 

 throughout Britain in large sheets ot" water where there is 

 little vegetation. 



K T I F E R A, 



Asjilanchna jiriodonta^ Gos.se. 



Asplanchna priodimta, Gosse, Ann. & Mag. Nat. Hist. ser. 2, vol. vi. 

 1850, p. 18, pis. i, & ii. ; Hudson and Gosse, Rotifera, p. 123, 

 pi. xii. fig. 2. 



Gosse found this species not uncommon in the Ser- 

 pentine, Kensington Gardens, and in ponds and ditches 

 near Birmingham. It was very sparingly but generally 

 distributed in April, but in June occurred in vast quantities 

 in all the tow-nettings taken at the surface and moderate 

 depths. 



In the Map accompanying this j)a])er the areas of depth 

 are signified by dotted lines. 



The weather was calm and tine when the tow-nettings were 

 made in June, but there had been heavy rains a few days 

 before. 



The tow-nettings were confined to the middle and northern 

 portions of the lake. 



In the 10-fathom area six tow-nettings were made, and 

 were characterized by the presence of Polyphemus in greater 

 numbers than elsewhere, and the almost complete absence of 

 Leptodora and Bythotrephes (a few immature forms were 

 taken). 



In the 25-fathom area four tow-nettings were taken from 

 6 to 8 feet, in which Leptodora and Bythotrephes were fairly 

 common. 



In tiie 50- fathom area five tow-nettings were taken from 

 6 to 10 feetj and in these gatherings Leptodora and Bytho^ 

 trephes were very abundant. (It is worthy of note that 

 Leptodora and Bythotrephes very often occur together in 

 great abundance.) 



The remaining forms were distributed more or less univer- 

 sally over tlie portion of the lake examined. 



