J. L. BROOKS 105 



successful in the area; that is, chance appeared largely to deter- 

 mine the species to be found living together. The largest number 

 of species yet found simultaneously in a lake in North America 

 (or the world) are the six that lived in Aziscoos Lake, Maine. 

 The one species, parvula, which was not found in Aziscoos at 

 that time was one of the least common in the Maine lakes studied. 



CATAWPA 



PARVULA RETROCURVA 



OUBIA 



GALEATA 



MENOOTAE 



AMBIGUA 



LONGIREMIS 



ABREPTOR, 

 FEMALE 



ABREPTOR, 

 MALE 



ANTENNULE, 

 MALE 



POSTABDOMINAL 

 CLAW 



FREQUENCY IN 107 

 MAINE LAKES 



LARGEST ASSOCIATION 

 (AZISCOOS LAKE) 



UPPER WATERS 



BOTTOM WATERS 



90 



10 



40 



33 



33 



10 



25 



Fig. 8. Species of Daphnia commonly occurring in New England lakes. 

 Most lakes have more than one species common at any time. The largest 

 association found was in Aziscoos Lake, Maine, which had the six species 

 indicated. Characteristic morphological and ecological traits of each species 

 are indicated. 



Although the coexistence of this many closely related species 

 raises many interesting theoretical questions (which will be 

 discussed elsewhere), our immediate interest is in the effect on 

 the problems of species recognition. The confusion which the 

 presence of as many as four or six species in a lake presents for 



