THE GENUS LEBERTIA. 499 



pores, ranging in the female up to sixteen, and in the male up to 

 twenty-five. 



Nymph. 



The nymphs are about 0*60 mm. in length and 050 mm. in 

 breadth. The fifth segment of the second pair of legs has two 

 swimming hairs. The fourth segment of the third and fourth 

 pair of legs has only two swimming hairs, and the fifth segment 

 only four swimming hairs. The flexor surface of the sixth 

 segment of the fourth pair of legs has only one small spine. 



This species has been found in Great Britain and Ireland, as 

 well as Norway, Sweden, Finland, Germany, Switzerland and 

 Italy. 



Lebertia vigintimacidata Sig Thor is now considered by its 

 author to be merely a variety of the above and other species 

 (vide. Zool. Anz., xxix. 786). 



Lebertia porosa Sig Thor. 

 (Sub-gen. Pilolebertia.) 



1897. L. tau-insignita et insignis Thor. Ark. Math. Naturv., xix. 



(6) 31 ; xx. (3) 18. 

 1900. L. porosa Thor. Nyt. Mag. Naturv., xxxviii. 273. 

 1905. Sig Thor, Zool. Anz., xxix. 761. 



Lebertia porosa is one of the species attaining a large 

 size. Considerable variation appears to exist with regard to 

 length, as specimens have been recorded from 0'9 mm. up to 

 2 - l mm., with a corresponding breadth varying from 85 mm. 

 to 1'9 mm. The most common length appears to be about 1 mm. 

 or a little over, and the breadth about 01 mm. less than the 

 length. The body is oval to almost round, frequently slightly 

 dorso-ventrally compressed. The anterior end is rounded, with 

 the apices of the first and second pairs of epimera extending 

 a little beyond it. The colour is a dark reddish brown or a 

 yellowish red with brown spots, with the excretory organ showing 

 through as a bright-yellow T-shaped dorsal figure. The epimera 

 may show a faint bluish or greenish tinge, while the palpi and 

 legs are more transparent, and evidently more variable as to 

 colour, as red, green, blue, or bluish green are found. Thor has 

 pointed out that the action of preservative solutions on the 



