218 
good preparations of all the species I have met with. Among 
forms difficult to prepare I maj name: Tylenchus , Plectus , Ce- 
phalobus and the smaller species of Diplogaster and Rhabditis. On 
the whole the larger forms seem to give the best results on pre- 
paration, especially the Dorylaimi. 
Monohystera dispar Bastian. 
1865. Bastian, 1. c. p. 97. PI. IX. fig. 1 and 2. 
1873. Btitschli, — p. 63. Tf. IV. fig. 24 a and b. (M. crassa). 
1884. de Man, — p. 41. Tf. III. fig. 12. 
I have this species, whose male is not known, only from the 
lake of Furesø, where it was taken quite near the bank and in 
the very edge of the water on roots of plants. I have only seen 
a few specimens; it seems not to £be so common in this country 
as it is in Holland according to de Man. The individuals also 
appear to be a little smaller. The length of the specimens, I have 
measured, is 0,4—0,7 mm. I note here the dimensions of a 
mature female that had one egg in the uterus; it was taken in 
August 1900. 
Zeiss O k ularm i krom., Obj. C. O c. 2. 
Length 87 = 0,57 mm. 
Oesophag. 19. 
Vulva 55. 
Tail 15. 
Breadth 4. 
The formula of de Man gives: a= 22, ft — 4 1 / 2 , y — 6. 
Mon okyster ft socialis Btitschli. 
1874. Btitschli, p. 28. Tf. II. figg. 8 a—d. 
Btitschli found this species very abundant in a brackish- 
water basin named „kleinen Kiel u in the town of Kiel. Here the 
animal lives essentially in the masses of Oscillaria. Btitschli 
tells how, taking dumps of Oscillaria with water in a glass, he 
saw a great number of the named species „wie Spinnweben zwischen 
