233 
in a pool in Dyrehaven near Springforbi. In Jntland it was taken 
in a trencli between Nørre Nebel and Nymindegab with very fer- 
ruginous water. 
While the male of I. ignavus occurs abont as abundantlv as the 
female this is not the case with I. longicaudatus ; though I have 
colleeted a lot of specimens I have not met with a single male. 
I give the measurements for a female with two eggs in the 
uterus. 
Zeiss Okularmikrom. A. Oc. 2. 
Length 166 = 1,2 mm. 
Oes. 26. 
Tail 40. 
Vulva 66. 
Phar. eavitv 7. 
Width 4. 
The formula of de Man givos: « = 41, = 6^2, r — 4. 
Trilobus gradlis Bastian. 
PI. III. figs. 16 and 20. 
1865. Bastian, p. 99. PI. IX. fig. 20—22. 
1873. Biitschli, p. 53. T. IV. fig. 21 a—e, 23 a—b. 
1884. De Man, p. 75. T. XI. fig. 43. 
This exceedingly nice Nematode occurs in this country abundantly 
in Furesø and Lyngby Sø. A single specimen has been taken in 
the Bøllemose near Skodsborg. It appears as if the specimens 
from the Furesø generally are a little larger than those from other 
localities; they have been taken in the edge of the water on roots 
of plants and often attain a length of 3 mm. 
In one female specimen I have found a peculiar monstrosity: 
The animal had two eggs in the uterus, one antevaginal and one 
postvaginal. But between the vulva and the anus occur four well 
developed masculine papillæ of the shape characteristic for the 
males of this species and in no respect to be distinguished from these. 
No spicules are found and, as far as can be seen, no testes; apart 
