736 THE AMERICAN NATURALIST [Vol. XLIV 



only later becomes visible. All the eggs of a mass 

 either die or develop properly; one or two of the eggs 

 may prove exceptions to this, but whatever the defect 

 may be it involves practically all the eggs of a bunch. 

 Whether it may extend to all the eggs of a female it has 

 not been possible to determine. This loss has also been 

 observed in spawn of A. jeffersoniamtm from a second 

 locality and is not likely to be due to any quality of the 

 water, for in the pools of each locality spawn of A. punc- 

 tatum has been found developing with very little loss, 

 and that apparently due to infection by fungus. Neither 

 can it be ascribed to low temperatures from early de- 

 position, for the earliest is no more liable to die than 

 that which conies later along with or after the spawn of. 

 A. punctatum. 



Larva 



Spawn of A. jeffersonianum brought to the laboratory 

 has been .allowed to develop and the larvae fed until the 

 larger specimens had attained a length of 30-40 mm. 

 In these it has been possible to detect a peculiarity of 

 marking not present in similar larvae of A. punctatum. 

 This peculiarity consists of a massing of dark chromato- 

 phores into three or four spots placed in a row along 

 each side of the mid-dorsal line, giving the animal, when 

 viewed from above, the appearance of being banded 

 (Fig. 2). Viewed from the side the same can be de- 

 tected, but is less conspicuous (Fig. 3). Incipient band- 

 ing is often indicated as soon as the chromatospheres 

 are well differentiated (Fig. 4). „, 



In looking over a large number of larvae all gradations 

 will be found between individuals in which the above 

 shows distinctly and those in which it is impossible to 

 detect it. For example, in 115 laboratory-reared larvae 

 examined at one time, 80 (69 per cent.) showed the dis- 

 tinctive marking. Of the balance, some individuals 

 under different conditions showed it also (either ex- 

 treme expansion or contraction of the chromatophores 

 obscures the pattern), but some never did. Exact num- 

 bers for this division of the 31 per cent, are not available. 



