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LIBBIE H. HYMAN 



13). The gradient of Lumbriculus is not very steep, except 

 at the anterior end, and slight variations, which seem to be 

 related to temporarily increased muscular activity, often occur. 

 Thus if the worm happens to coil itself, the coiled part may show 

 slightly increased susceptibility as compared with surrounding 

 parts, which may be explained as due to contraction of muscles 

 in coiling. Such variations become apparent in a slightly slop- 

 ing gradient but are concealed in steep gradients such as occur 

 in the naids. The slight slope of the gradient of Lumbriculus 

 indicates a low degree of correlation. 



Fig. 13 Graph of the axial gradient of Lumbriculus inconstans. 



5. The gradient of the tuhificids 



In the tubificids, the posterior rise in metabolic rate has pro- 

 ceeded to a maximum extent. The forms used were Tubifex 

 tubifex and Limnodrilus claparedianus, and the concentration of 

 cyanide about ^?o. Disintegration always begins at the pos- 

 terior end and proceeds far forward before the head begins to 

 disintegrate. The disintegration proceeds very slowly back 

 from the anterior end and meets the posterior disintegration 

 somewhere between the fifth and the fifteenth segments of the 

 body (figs. 14 and 15). 



6. The gradient in embryos 



Before concluding this section, I should like to speak briefly 

 of the gradient of the annelid egg and embryo. Child ('14 a) 

 has worked with the eggs of Chaetoperus and Nereis, and found 



