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THE AMERICAN NATURALIST 



[Vol. XLII 



above and behind the eye the nasal pit still forms and the olfac- 

 tory fibers which develop in it grow into the lateral wall of the 

 diencephalon above the eye, which is of course an unusual region 

 for these nerve fibers to enter. 



C. E. Stockard. 



The Influence of Regeneration on Moulting in Crustacea. — A re- 

 cent paper by Dr. Margarete Zuelzer 1 furnishes additional data 

 regarding the influences of regeneration, or the replacement of 

 lost parts, on the moulting process in Crustacea. It is generally 

 known that the members of this group have the power to grow 

 new appendages, legs, antennae or swimmerets, after the former 

 ones have been lost through accident or injury. In order to 

 produce the new limb as well as to grow, or increase in body 

 size, the crustacean must moult its hard chitinous shell. The 

 processes of growth are closely associated with moulting and 

 the more frequently the animal moults the faster will it in- 

 crease in size. When one of these animals has lost a limb it is 

 usually replaced by a small new one during the next moult fol- 

 lowing the injury. 



Since the moulting period is so closely connected with the 

 normal rate of growth several investigators have endeavored to 

 ascertain what effect regeneration might have on the interval 

 between these periods. Zeleny found that crayfish while regen- 

 erating their limbs moult faster, or more frequently, than normal 

 individuals, and. further, he holds that an animal regenerating 

 several limbs moults more frequently and regenerates the limbs 

 faster than one replacing a single appendage. He concludes 

 that during regeneration the moulting process is hastened. 

 Emmel, on the other hand, has reached an opposite conclusion 

 from the study of a large series of young lobsters. He finds 

 normal individuals moulting more frequently than others which 

 are regenerating new limbs. Lobsters that have lost several 

 appendages moult slower than those that have lost fewer. 

 Emmel, therefore, believes that regeneration retards the moulting 

 process. He showed very clearly that an important factor, 

 which Zeleny had failed to take into account, was the time at 

 which regeneration was introduced into the moulting cycle. 

 If the limbs were removed the day after moulting the moulting 

 period remained almost normal, but when the limbs were re- 

 moved four days after the moult the resulting regeneration 



1 Uber den Einfluss der Regeneration auf die Wachstumsgeschwindigkeit 

 von Asellus aquaticus L. Arch fiir Entwicl:-Mech., XXV, Dec, 1907. 



