i go 



LILLIE AND KNOIVLTON. 



[VOL. I. 



angle with the axis of the trunk generally inclined ventrally, 

 rarely dorsally, never laterally. 



4. General. 



This is the first time, I believe, that an attempt has been 

 made to represent in the form of a curve the effect of tem- 

 perature on the rate of development in animals, or that suf- 

 ficiently extensive observations have been made to render this 

 possible. The literature on the subject is mostly old and of 

 historic interest only ; the principal papers are cited in the 

 list of literature. A good and detailed discussion of it is to be 

 found in chapter V of Preyer's PJiysiologie des Embryo ('85). 



But there have been more extensive observations on the 

 influence of temperature on the rate of growth in plants. The 

 following table, taken from Vines ('9l), p. 293, shows the incre- 

 ments in length of hypocotyls of various plants in forty-eight 

 hours after Koppen and de Vries. 



TABLE IX. Increment in length of hypocotyls in 48 hours, from Vines ('86), p. 293. 



These figures are strikingly different in the relation of the 

 maximum to the optimum from those which we have found 



