KTJNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 63. N:0 7. 



15 



Table showing the openings of the nephridia (O) and the normal position of the triangulär 

 glandular field (a) in the 4 Leiochone species in question; in addition there is given information about 

 5 abnormal specimens (I — V) of L. johnstoni; + indicates the presence of setae (capillary setae and 

 uncini). 











Leiochone 



johnstoni 







L. leio- 

 pygos 



L. po- 

 laris 



L. bo- 

 realis 



Setige- 

 rous seg- 

 ment 



Normal 

 specimen 



Spec. I 



Setige- 

 rous seg- 

 ment 



Spec. II 



Spec. III 



Spec. IV 



Spec. V 



no. 







no. 





























1. 



r. 



1. r. 









1 



+ 



+ 



1 



la 



+ 

 + 



+ 



4- 



+ 



capillary 

 setae 



capillary 

 setae 



+ + 



capillary 

 setae 









2 







2 

















3 







3 

















4 







4 

















5 







5 

















6 



O 



O 



6 



O 



o 



O 



O 



O 



O 



O 



7 



o 



o 



7 



o 



o 



o 



o 



o 



o 



o 



8 



Oa 



O* 



8 



OA 



Oa 



Oa 



OA 



OA 



Oa 



Oa 



9 



O 



O* 



9 



o 



O 



O 



o 



o 



O 



O 



10 



O 



o 



10 



o 



O 



O 



o 





O 





11 







11 



















The second group of diverging specimens (ef. nos. II — V in the table above) is of far greater interest 

 as distinguished by the occurrence of 6 more or less distinct setigerous segments in front of the fore- 

 most nepbridia-bearing segment (in normal cases the 6 th setigerous segment, and looked upon as 

 such in the table for these specimens as well). No extra lower triangulär glandular field is observed. 

 Inasmuch as the normal one occurs on the 3 rd nephridia-bearing segment, it is by far more probable 

 that the existing triangulär glandular field does not correspond to the posterior but to the anterior 

 field, situated on the 8 th setigerous segment in specimen no. I in the table above. In other words 

 we must assume the occurrence of a supernumerary anterior setigerous segment in these specimens. 

 As the specimens in question are unfortunately incomplete, it is not possible to decide whether the 

 occurrence of an extra anterior segment had any effect on the number of segments in the posterior 

 division of the body (ef. a case observed in Nicomache lumbricalis var. borealis [24, p. 96], in which the 

 anterior body had a supernumerary segment, while the posterior body had one segment too little). 



Specimen no. II in the table, from Balloch Sands, has the l sfc setigerous segment and the an- 

 terior part in front of it normal; the l st setigerous segment has capillary setae and 2 — 3 uncini on 

 each side. The next segment, 1 a in the table, is long and furnished with strongly developed setae. 



Specimen no. III in the table, from Great Cumbrae Island, greatly resembles the previous 

 one; see fig. 11. 



Specimen no. IV in the table, from Great Cumbrae Island, resembles the previous one but the 

 segment following the l Bt setigerous segment, i. e. setigerous segment 1 a of the table, is rather short 

 and the anterior glandular ring is developed only on the left side. The l st setigerous segment lacks 

 uncini on the right side, on the left side there is one uncinus; segment 1 a has only capillary setae 

 and these are little developed on the right side. There are further before me two similar, though 

 still more irregularly developed specimens, one of which is dealt with in more detail as no. V of the 

 table. This specimen, from Balloch Sands, has the anterior end in front of the l st setigerous seg- 

 ment normally developed; this l 9t setigerous segment is, however, rather short and looks asif divided 



