154 The Ohio Journal of Science [Vol. XXI, No. 5, 



Simocephalus vetulus (O. F. Miiller), said to be "not ver}^ 

 abundant," but likely to be found anywhere where vegetation 

 thrives, was found decidedly more common here and at more 

 places in the small pond. 



Order Copepoda. 



This order, though with a smaller number of specimens 

 collected, was somewhat better represented in species than 

 Cladocera. Similarly there may have been limnetic forms 

 entirely missed. 



Cyclops bicuspidatus Claus, was the species most numerous 

 in individuals and ranked as common. As Marsh noted it has 

 its optimum in cold water, and all specimens were taken from 

 Mirror Lake early in spring, none after April 16, when the 

 temperature was 14° C. At the next collection. May 3, the 

 temperature of the water was 16° C. 



Cyclops albidus Jurine, was much less common; only a 

 third as many as of C. biciispidatiis, were collected. 



Cyclops serrulatus Fisher, was not uncommon and ranked 

 midway in numbers of individuals between the other two 

 species, as far as the collection could show. 



Subclass Malacostraca. 



Order Isopoda. 



Family Asellidcs. 



Asellus was found quite common, and almost exclusively 

 in the waters of the small pond together with the spring, sta- 

 tion 13. It was found in masses of submerged algse, on Lemna 

 roots, debris and on the bottom. 



Why nearly half of all Asellus material was secured from 

 this spring, is not clear. There was less vegetation in it than in 

 the pond, hence less food, and the bottom was no better. The 

 temperature conditions might explain it. The temperature of 

 the water in the spring from May 17, when the first collection 

 was made there, to Oct. 4, was from 1° C. to 5° C. colder than 

 in the pond. The most difference occurred in June; the least 

 in October. At every collection in this period specimens were 

 found in the spring and pond. On October 18, (date of the last 

 collection) Asellus was found in the spring only, and the tem- 

 perature of the water there was 2° C. higher than in the pond; 

 but since the water in the pond was 7° C. colder than at the 



