C. M. CHILD. 



apparently occurs when the stolon is not very active and the 

 gradient is therefore short. Under such conditions the tip is 

 apparently able to obtain nutrition only from regions within a 

 short distance. The region in which atrophy occurs evidently 

 represents approximately the limit of this distance. 



In the earlier stages of this process of growth during starvation 

 the development of hydranth-stem axes from such stolons may be 

 induced by providing optimal conditions, but in later stages this 

 transformation occurs less frequently and with the approach of 

 exhaustion, but before stolon growth ceases, all attempts to induce 

 transformation have thus far failed. 



This continued growth of the stolon tip at the expense of the 

 larval body and later of its own substance is an interesting case of 

 a more active region maintaining itself at the expense of less 

 active regions. Whether the atrophy of the less active regions 

 represents primarily a more rapid autolysis or some other process, 

 it is clearly evident that the most active region, the high end of 

 the stolon gradient, succeeds in using the substance of all other 

 levels, not only for maintenance, but for growth. Such stolons 

 may grow over a distance of 10-15 centimeters before exhaustion 

 occurs. Doubtless each stolon level lives at the expense of levels 

 below it and sooner or later becomes a source of nutrition to levels 

 above it in the gradient. This relation may mean simply that 

 less active regions undergo autolysis more rapidly and that the 

 more active regions are able because of their activity to use the 

 products of autolysis in maintenance and even in growth. 



A similar relation between different levels of the axial gradient 

 appears in other cases of reduction by starvation. For example, 

 in planarians and other forms undergoing reduction the propor- 

 tions approach those of younger animals because the higher 

 levels of the polar gradient, particularly the head region, maintain 

 themselves to some extent at the expense of lower levels and so 

 undergo reduction less rapidly than those. 



EXPERIMENTAL RECORDS. 



The uniformity of result makes it entirely unnecessary to give 

 the records of all experiments in full. A lew characteristic 

 records are given in Table I. as examples. Other records differ 

 from these only as these differ from each other, i.e., in degree and 



