Morphological J'ariation and Its Causes in A. tigrinum 75 



EXPLANATION OF PLATES 



All figures are from photographs, % natural size. All are from living 

 animals anesthetized with chloretone, unless otherwise stated. Color pat- 

 terns (to be treated elsewhere) are nearly true to the originals. 



Plate I 



Fig. 1. Side view of very compact larva ; form due to rapid growth with 

 little swimming. 



Fig. 2. Side view of larva shortly before metamorphosis ; form due to 

 less rapid growth. ^ 



Fig. 3. Side view of larva of typical form, due to free-swimming habit 

 and rapid growth. 



Plate II 



Fig. 1. From formalin specimen. Shows excessive development of paro- 

 tid glands due to brief period of maximum nutrition. The special visibil- 

 ity of glandular pores due partially to state of preservation. 



Fig. 2. Dorsal view of larva from same lot as fig. 1 of pi. I. Shows 

 the short form due to growth with little locomotion, and wide head due to 

 expansion of head by feeding on daphnids in the dark, and to moderate 

 development of parotids. 



Fig. 3. Side view of head of fig. 2. 



Fig. 4. Dorsal view of slender larva, result of slow growth with swim- 

 ming habit. 



Fig. 5. Partial side view of fig. 4. 



Fig. 6. Posterior foot of a medium to slowly-grown larva about 20 cm. 

 in length. 



Fig. 7. Posterior foot of a 25 cm. , larva, very slowly, grown. 



Fig. S. Posterior feet and limbs of a 20 cm. larva, very rapidly grown. 



Fig. 9. Posterior foot and limb of a 27 cm. larva slowly grown. 



Fig. 10. Posterior foot of 27 cm. sexually mature larva of robust and 

 rapid growth. 



Figs. 11, 12. Posterior foot of rapidly grown specimen photographed 

 before and after metamorphosis, showing full retention of form and flat- 

 tened digits. 



Plate III 



Fig. 1. Slender, narrow-tailed adult resulting from a slowly grown larva. 

 Fig. 2. Short, broad-tailed adult resulting from rapid growth. Same 

 as larva, fig. 1, pi. I. 



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