zones, are also well distributed in the marginal 

 zone. Perhaps the former species is less capable of 

 accommodating itself to different environments than 

 the latter two; in proof of this, witness its absence 

 from all marginal stations at the eastern end of the 

 lake. The remaining species, D. minutus, was 

 found at only 3 stations, Stony Point, Portage River, 

 and Conneaut, all on the American shore at the mid- 

 dle and western end of the lake. It had been report- 

 ed previously from the lake but was not found at the 

 eastern end during 1928. 



Epischura occurred in 23 of the marginal sta- 

 tions and in half of them it was abundant or common. 

 This large copepod is usually considered as an open 

 water or deep water form, and its presence in con- 

 siderable numbers among the aquatic plants and in 

 the ponds of the lake drainage was somewhat of a 

 surprise. Only a single specimen of Limnocalanus 

 was found in the marginal zone and that was after a 

 heavy wind had been blowing on shore for 2 days so 

 that its presence was probably casual. 



Cladocera 



Daphnia and Sida were present in considerable 

 abundance at about two-thirds of the localities ex- 

 amined, and were evidently breeding at some of 

 them. The varieties of the species D. longispina 

 were far more numerous and more widely distributed 

 in this zone than those of p. pulex. Diaphanosom a 

 and Leptodora were next in abundance, the former 

 in the middle and western end of the lake, the lat- 

 ter especially in Sandusky Bay and in the mouths of 

 Cattaraugus and Eighteen Mile Creeks. Acroperus, 

 Camptocercu s, Chydor us, Scapholeberis, and 

 Simocephalus are the only other cladocerans that 

 are worthy of mention, the remaining species being 

 well distributed but in small numbers. Attention is 

 called, however, to Leydi gia acanthocercoides which 

 is listed by Ward and Whipple (1918) as "Rare; 

 Louisiana. " It was found at 5 localities in the lake, 

 and at Turkey Point on the Canadian shore it was 

 quite abundant together with Sida. 



Other Crustacea 



In addition to the Entomostraca species of 

 Gammarus , Hyallella, and Palaemonetes were found 

 at most of the stations. One or more of these usu- 

 ally occurred in sufficient numbers to make them of 



considerable value as fish food, supplementing the 

 copepods and cladocerans. This was especially true 

 amont the water plants along the Canadian shore 

 and at the 3 larger breeding areas previously de- 

 scribed. Ostracods were found at nearly all the sta- 

 tions, but in very small numbers except at Crescent 

 Beach and Point Abino where they were abundant. 



Other organisms 



Damselfly and dragonfly nymphs and various 

 fly larvae were found at nearly every locality in the 

 marginal zone, often in considerable abundance. 

 Caddisfly and mosquito larvae were also present 

 nearly everywhere, but in much smaller numbers; 

 beetle larvae and mayfly nymphs were rarely found. 

 Besides the insects, 2 species of Hydra were fairly 

 common, H. fuse a being well distributed along both 

 sides of the lake throughout its entire length, but 

 H. viridis being confined to the American shore at 

 the eastern end and to the ponds of the lake drainage. 



Resume of Marginal Zone Plankton 



One general feature of the marginal plankton is 

 worthy of special emphasis, namely that both its 

 copepods and cladocerans showed a greater disparity 

 of distribution than those of the other two zones. Near- 

 ly every station yielded 1 or 2 species in abundance, 

 while all the others were more or less incidental, and 

 only rarely were the abundant species the same at ad- 

 jacent stations. 



This zone was characterized positively by 5 

 species of Cyclops . C. albidus, C. fuscus , C. 

 phaleratus , C. prasinus, and C. viridis; by 1 species 

 of Diaptomus , D. minutus ; and by 42 cladoceran 

 species. Limnocalanus, Holopedium , Mysis, and 

 Pontoporeia were absent. 



LITTORAL AND LACUSTRIC ZONES 



Littoral Zone 



This zone includes the shallow water from 1 to 

 10 meters in depth and overlaps the marginal zone 

 toward the shore and the lacustric zone toward the 

 middle of the lake. In June and July, 1928, this 

 zone was covered by the steamer Navette, which was 

 small enough to enter quite shallow water. In the 

 meter net hauls of this zone, 2 copepod and 2 cla- 



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