APPENDIX I 



Some further consideration of methods of determining respiration, as used in 

 attempts to discover whether regional respiratory differences are present along the 

 polar axis and of objections and criticisms advanced and the grounds on which they 

 are based, will perhaps serve to show more clearly some of the difficulties involved and 

 the precautions necessary in the use of the methods in this way. 



In an attempt to determine whether respiratory gradients exist, Shearer (1924) 

 stated that there are serious objections to the Winkler method but did not say what 

 they are. Parker (1929, p. 422) agrees with Shearer but also fails to state what the 

 objections are. In a later paper Shearer (1930, p. 264) says that the error resulting 

 from the discharge of slime and tissue fluids into the water is always very great where 

 a large number of animals is employed, but he presents no data to confirm his asser- 

 tion or to show how great the error may be. In fact, there is no evidence in these papers 

 to show that either Shearer or Parker has ever used the Winkler method. Needham 

 (1931, p. 586) also questions the value of data obtained by Hyman with the Winkler 

 method on the basis of a personal statement of opinion by Shearer, but again without 

 presenting any evidence in support of his view. These somewhat dogmatic expressions 

 of opinion without evidence to support them can scarcely be regarded as valid scientific 

 criticism and are certainly an inadequate basis for discarding a large body of highly 

 consistent positive data. Moreover, in the use of the Winkler method in connection 

 with the gradient problem the relative, rather than the absolute, rates of oxygen con- 

 sumption of similar pieces from different body-levels, or of the same pieces at different 

 times, are the important data. Since equal, or approximately equal, numbers of pieces 

 and equal test periods have been used in lots to be compared, any possible error due 

 to slime production or other substances from the pieces should be approximately the 

 same in different lots. Actually, however, pieces of Dugesia dorotocephala used in 

 many determinations do not produce large quantities of shme when undisturbed in 

 normal environment, as they are during respiratory periods for Winkler determina- 

 tions; and any slime that is produced does not immediately spread through the water 

 but remains on the wall of the container, or, in the case of small pieces which do not 

 move about, it may form an envelope about the piece resembling a cyst, and the piece 

 may remain in it for several days. Samples of water taken from the container for analy- 

 sis contain httle or none of this slime. Cut surfaces of planarian pieces, hydroids, and 

 other forms contract rapidly after section, so that the discharge of tissue fluids occurs 

 only during a short time. With planarian and hydroid pieces the contraction occurs 

 before the pieces can be made ready for the respiratory period; moreover, determina- 

 tions were made not only soon after section but also several hours later. Attention 

 was particularly called to these points by Hyman (19166) on first using the Winkler 

 method, and determinations have been made repeatedly, showing that error from these 

 sources is negligible (Hyman, 193207). The criticisms of Shearer and Needham are with- 

 out foundation. As regards the question of possible nitrite error in Winkler determina- 



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