DORSAL BLOODVESSEL OF THE EARTHWORM. 273 



Ki and K indicate the rates in contractions per minute at the 

 temperatures 7\ and T^ respectively, in degrees Centigrade. 



If \ve arrange the data of Table I. so as to show the relation 

 existing between the higher and lower temperature ranges and 

 the value of <2io we have evidence that for the lower temperatures 

 there is a higher coefficient than for the higher ranges. This 

 fact is not so clearly shown in the case of the earthworm as in 

 some of the forms already studied, probably for the reason that 

 it is very difficult to count the beats of the dorsal blood vessel 

 of the earthworm at temperatures below 8 C. The movements 

 of the walls are so feeble and so slow that one is not sure when a 

 contraction has taken place. 



TABLE II. 



71. TO. Number of Worms. Average fio. 



About 27 to about 14 4 1.671 



" 27 " " 12 2 1.536 



26 " 11 4 1.292 



" 25 " " 13 3 1.725 



" 22 " " I 3 6 2.IQ9 



" 21 " " 13 2 2.533 



" 20 " " 9 2 1.728 



" 16 " " 11 6 2.919 



In Table II. we have such an arrangement of the data as 

 suggested in the preceding paragraph. It will be noted that 

 while in general the coefficients for the lower ranges are higher 

 than those for the higher ranges of temperature, there are very 

 marked exceptions to the rule. The only explanation we have 

 to offer at this time for the rather marked variation from what 

 we should expect, if the beat of the dorsal blood vessel of the 

 earthworm is subject to the same laws as the beats of various 

 hearts already studied, is that we have here to deal with a series 

 of nervous effects which must be in some way eliminated in 

 order to avoid complications. Up to the present time we have 

 not found any means of avoiding these nervous effects in the 

 worm, though in fish embryos where the rate of heart beat was 

 studied before the nervous connections were established it was 

 found that one could predict with some degree of certainty what 

 the rate of heart contraction should be at any stated temperature. 



