Morphological J'ai'iation and Its Causes in A. tigrinnni yj 



Plate VI 



Fig. 1. Slender headed adult with extremelj' small gape of mouth. Re- 

 sult of larva fed excessively on daphnids, in clear water, with continuous 

 free-swimming habit. 



Fig. 2. Adult showing maximum broadening of head by aquatic life. 

 Also corrugated dorsum of tail. 



Fig. 3. Head of large larva showing truncated muzzle. 



Figs. 4, .5. Heads of adults showing truncated muzzles developed during, 

 aquatic life of adults. 



Plate VH 



Figs. 1, 2. Profile and dorsal views of large cannibal larva. Preserved 

 specimen. 



Fig. 3. Dorsal view of normal larva of nearly same length as the can- 

 nibal. Preserved specimen. 



Fig. 4. Dorsal view of head of adult (compare profile, fig. 3, pi. HI) 

 resulting from a semicannibal. Formalin preservation. 



Plate VHI 



Fig. 1. Young cannibal after full meal. Formalin. 

 Fig. 2. Typical larva — daphnid-feeder. Formalin. 

 Fig. 3. Typical young cannibal, dorsal view. Formalin. 

 Fig. 4. Typical young cannibal, ventral view. Formalin. 

 Fig. 5. Typical young cannibal, side view. Formalin. 

 Fig. 6. Normal larva, typical of the ordinary specimens among which 

 the cannibals were found. 



Plate IX 



Fig. 1. Broad-headed larva of transition type, i. e. a partially reformed 

 cannibal. Formalin. 



Fig. 2. Head of large wild adult assumed to result from larva like fig. 

 1. Formalin. 



Fig. 3. Head of transition type due to partial cannibalism. 



Fig. 4. Larva showing slight modification in form of head, due to brief 

 assumption of cannibalistic habits. 



Fig. 5. Slender larva of type from which fig. 4 was produced. 



Fig. 6. Young cannibal showing condition of emaciation in which this 

 type is frequently found. Formalin. 



Fig. 7. Somewhat aberrant type of young cannibal. Formalin. 



Fig. 8. A young transition type or semicannibal due to double habits of 

 feeding. Formalin. 



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