Copepod Fauna of the ““Maare”’ of the Eifel. 297 
the basal joint. In the last quarter of it, on the outer 
margin, 1s seated a spine which is as long as the joint. 
At the apex is geniculated a spine formed by the transfor- 
mation of the third joint of the ramus, which is at least as 
long as the three preceding joints. At its base it is dilated 
into a vesicular form, and about the middle it makes a 
bend, so that its two halves stand nearly at right angles 
to each other. The one-jointed inner ramus bears some 
fine hairs at the extremity. ‘he left rudimentary foot of 
the male is a little shorter than the right one. The basal 
joint is larger than that of the right foot. he apex of the 
second joint is produced into a short stiff spine, close to which, 
on the inside, another more slender one is attached. In the 
small ovisac I always found only two eggs. The length of 
the female including the caudal setz is 1 millim. and that of 
the male 0-8—0°9 millim., or rather less than found by Lillje- 
borg. 
This species comes very near Diaptomus gracilis, Sars, and 
it is quite possible that it is only a form of that species pro- 
duced by adaptation and isolation. I have obtained, also from 
Dr. Zacharias, an abundance of Diaptomus gracilis from the 
‘““Faulen See,” near Frankfort on the Oder. Some of the 
specimens of normal size showed small variations which 
partly agree with the characters of Diaptomus graciloides. I 
hope shortly to be able to make a more exact investigation of 
these conditions, by which, perhaps, some light may be 
thrown upon the causes of the variations. Diaptomus gracil- 
oides was found by Lilljeborg chiefly in the great freshwater 
lakes of Sweden and the Russian Kola peninsula to near the 
shores of the northern icy sea. 
Of all the species cited from the ‘‘ Gemiinder Maar” I 
obtained only very few sexually mature animals, and espe- 
cially in the case of the Déaptomus I had much trouble in 
finding in the rich material a sufficient number of adult speci- 
mens tor the investigation. 
All the Copepoda were strongly coloured red, the Déiap- 
tomus most intensely. The colouring-matter was chiefly 
combined with fat and could be extracted with this by ether. 
The group of the Copepoda inhabiting the 
IIT. HotzMaar 
is again differently constituted from that in the fauna of the 
two “* Maare ” described. There are still the three Cyclopidee 
found in all the *‘ Maare 7’ :— 
