SOME FURTHER RECORDS CONCERNING THE 



PHYSIOLOGY OF REGENERATION IN 



TUBULARIA. 



T. H. MORGAN. 



The following experiments are in the main continuations of 

 previous ones carried out to test further certain results whose 

 interpretation was in doubt owing to insufficient data. The main 

 problem concerned the influence of regeneration at the oral end 

 on the rate of regeneration at the basal end. Experience shows 

 that caution must be used in interpreting the experiments that 

 bear on this point, because, in the first place, the rate of regen- 

 eration is greatly influenced by slight changes in temperature, 

 and therefore accurate results along these lines should be carried 

 out in the future in water kept at a uniform temperature. The dif- 

 ference of temperature of day and night is a serious obstacle when 

 dishes are kept at room temperature. In the second place the 

 aeration of the water is also an important factor and should be 

 controlled. The extent of surface exposure of the water, the num- 

 ber of pieces in a dish, and the number of other' organisms attached 

 to the stems, also influence the time of regeneration, in the latter 

 cases by utilizing the oxygen or by fouling the water. In the third 

 place there can be little doubt that an internal " condition " of the 

 colonies plays a role in the result. Control pieces from the same 

 colony s iould always be present, but even this precaution is not 

 entirely sufficient, since different stems of the same colony may 

 differ in their internal conditions. 



Despite these difficulties some general conclusions may be 

 drawn, although certain of the experiments will be more profitable 

 when the external conditions are more fully controlled. By 

 keeping the dishes surrounded by running water I have met 

 some of these difficulties in many of the experiments where rate 

 of regeneration is involved. 



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