The Copepod Fauna of the "Maare " of the Eifel. 293 



XXXIX. — The Copepod Fauna of the "Maare " of the Eifel. 

 By JJr. Julius Vosseler *. 



Since Leydig's f investigations upon the fauna of the crater- 

 lakes of the Eifel, the so-called " Maare," scarcely any natu- 

 ralist has given any close attention to the lower animal world 

 of those basins. Of the lower Crustacea only the Cladocera 

 were investigated to some extent, while of the Copepoda only 

 tlie occurrence of Ci/clops in several lakes was mentioned. 

 When in August of last year Dr. O. Zacharias J undertook 

 the study of the microfauna of these waters, which are inter- 

 esting in many ways, I took upon myself the task of working 

 up the Copepoda, and the more willingly as in so doing 

 valuable information upon the distribution of species, the 

 adaptability of the group under consideration, and various other 

 interesting questions was to be expected. 



As Dr. Zacharias was permitted to make his captures in 

 part by means of a boat (on tlie Laacher See and Gemlinder 

 Maar), and, further, the pelagic fauna was pursued also at 

 night, the following catalogue may furnish, at least for that 

 time of the year, a tolerably complete picture of the distribu- 

 tion of the species and genera of Copepoda in the " Maare." 

 The greatest number of species is harboured in the 



I. Laacher See. 



By far the greater part of the Copepoda found here belong 

 to the littoral fauna. Of Cyclopidee the material placed at 

 my disposal contained : — 



1. Cyclops viridis^ Fischer; 



2. tenuicormsy Claus; 



3. signatusj Koch ; 



and of these three large species Cyclops viridis was the most 

 abundant. Most of the animals were adult, but ovisacs only 

 occurred very rarely in the females. The most numerously 

 represented was 



* Translated from the ' Archiv fiir Naturgeschichte,' Jahrg. 55, Bd. i. 

 p. 117, Tafel vi. 



t ' Verhandl. Ver. d. preuss. Rheinlande und Westfalen,' Jahrg. 37 

 (1881). 



X See his " Bericht liber eiue zoolog. Exkursion an die Ki'aterseen der 

 Eifel " (Biol. Centrallb. Bd. ix. 1889), to which this paper forms a supple- 

 ment. 



