Physiology of Reproduction in Domestic Fowl 357 



the muscular activity of the walls of the uterus determines the 

 shape of the egg. The results further show that this morphoge- 

 netic activity of the oviduct may be of a definitely regulatoiy char- 

 acter. 



Turning to the consideration of the regulation shown in this 

 case the chief point of interest lies in the precise manner in which 

 the regulatory change follows a logarithmic curve. Though the 

 biological processes involved are quite different in the two cases 

 the type of change is exactly the same in the successive produc- 

 tion of leaf whorls and branches in the normal ontogenetic devel- 

 opment and growth of Ceratophyllum (cf. p. 8 supra) and in the 

 successive production of eggs by this hen No. 183 which has been 

 seen to be a regulatory process in the strict sense. The approach 

 from a condition of wide deviation from a final type to that type 

 is in both cases along a logarithmic curve. This means that nor- 

 mal ontogenetic development and growth on the one hand, and 

 regulatory development on the other hand have at least one 

 character or principle in common. This principle may be 

 set forth as follows. Whenever a developmental or growth proc- 

 ess follows a logarithmic curve it means that the amount of 

 change which occurs in any given time interval, say between time 

 A and time B, is strictly proportional, either directly or inversely 

 to the total amount of change which has occurred before time A, 

 or, in other words, to the condition in which the organism finds it- 

 self at time A. Furthermore, the rate of change is proportional 

 to the time during which the process has continued. Thus to take 

 a concrete illustration, the amount of growth occurring in a time 

 period A to B in an organism exhibiting a logarithmic growth curve 

 is proportional to the size which the organism has already attained 

 at time A. In growth this relation is inverse: the larger the organ- 

 ism (i.e., the more it has grown) at any given time, the smaller 

 will be the growth change in the next subsequent unit time inter- 

 val. The longer the process contuiues and the nearer it comes to 

 its final goal, the slower is the rate of progression towards that goal. 

 It is of much interest to find both normal ontogenetic and regu- 

 latory changes alike in this respect. 



In the case of Ceratophyllum (Pearl '07) it was found that in 



