. The Canadian field-naturalist. 280 The Canadian Field-Naturalist Vol. 87 F /I '> ^ '^-'^ J^^ ^1 M -f^ 3 1 7___,1_. 1 l8___|2_^ 11 12 ! ' T^ 0 \ h B 1 1 1 4r 2; 2 2 2 ^4^ K ''"^ J 1 3 ilO 2 1 5 3 2 1 2 37 \ ^^^ ^ 2 7 1 3 21 ^22 1/' 1 1 10 ? 10 1 6 R 5 2 4 2 1 1 5 4 3 31 ^/i 5 3 2 26 6 27 2 1 5 19 6 6 V 4 1 1 1 1 3 5 6 25 3 56 3 1 12 6 3 10-Ao >^! 9 7 3 6 10 1 10 2 2 6 3 22 16 13 13 16 21 2 7 2 53 102 22 19 8 7 1 19 10/ R 'A ^ 4< U^ Ld 2 2 7 19 5 ^ V 8 12 50 21 20 8 2 3 1 4 / if ^ L U^ C7 V, E k. 2 k 5 1 A â ^ Water flow. 50 100 1 m Nuphar polysepala Submerged vegetation ; Po
. The Canadian field-naturalist. 280 The Canadian Field-Naturalist Vol. 87 F /I '> ^ '^-'^ J^^ ^1 M -f^ 3 1 7___,1_. 1 l8___|2_^ 11 12 ! ' T^ 0 \ h B 1 1 1 4r 2; 2 2 2 ^4^ K ''"^ J 1 3 ilO 2 1 5 3 2 1 2 37 \ ^^^ ^ 2 7 1 3 21 ^22 1/' 1 1 10 ? 10 1 6 R 5 2 4 2 1 1 5 4 3 31 ^/i 5 3 2 26 6 27 2 1 5 19 6 6 V 4 1 1 1 1 3 5 6 25 3 56 3 1 12 6 3 10-Ao >^! 9 7 3 6 10 1 10 2 2 6 3 22 16 13 13 16 21 2 7 2 53 102 22 19 8 7 1 19 10/ R 'A ^ 4< U^ Ld 2 2 7 19 5 ^ V 8 12 50 21 20 8 2 3 1 4 / if ^ L U^ C7 V, E k. 2 k 5 1 A â ^ Water flow. 50 100 1 m Nuphar polysepala Submerged vegetation ; Potamogeton natans & Equisetum sp. Dry areas nniD . Figure 1A (Lower map). Map of the seven "sub-habitats" defined for the bottom of Marion Lake. The areas termed "submerged vegetation" supported some of the following species: Chara globiilaris, Isoetes occiden- talis, and Potamogeton epihydris. The "open mud" habitats were defined in terms of the depth of water covering them. Figure IB (Upper map). Distribution of egg masses in Marion Lake in 1969 and 1970. The number in the upper right-hand corner of each quadrat indicates the number of egg masses found in that quadrat in 1969; the lower left-hand number indicates masses found in 1970. The quadrats shown are lOOC m^. anchored buoy at the corners of each quadrat. The shallow areas (less than 1 m in depth) were searched from a boat and each egg mass was marked with a stake. I searched the deeper areas by diving, and a systematic pattern was assured by following a boat which was rowed back and forth through the quadrat. The clarity of the water, the sparseness of the vegetation, and the large size (approximately 15 cm dia- meter) and opacity of the egg masses suggest that very few egg masses were missed. There is no species of plant in Marion Lake which is capable of obscuring an egg mass of the size laid by Rana aurora. Complete recounts of selected quadrats in both deep and shallow water result
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