1 -- C. M. CHILD. 



with high end at the tip. In Fig. 24 the basipetal gradient of 

 cytolysis in lethal concentrations is indicated in the three stolons. 

 When acclimation or recovery proceeds far enough, the tips of 

 such stolons sooner or later transform into hydranth-stem axes, 

 like the stolon of Fig. 19, or hydranth-stem axes arise as adven- 

 titious buds from their upper surfaces, as in Figs. 20 and 21. In 

 this way an individual which has been made apolar through 

 differential inhibition may develop during acclimation or recovery 

 several new stolon axes and each of these may later give rise to 

 several hydranth-stem axes. On the other hand, if acclimation 

 or recovery is only partial each stolon may continue to grow 

 indefinitely as a stolon until exhaustion occurs. 



THE GROWTH AND SEPARATION OF STOLONS. 



The continued growth of stolons under slightly inhibiting 

 conditions shows certain features of interest, some of which w r ere 

 briefly described in an earlier paper (Child, '23) as observed in 

 stolons arising from hydroid colonies in consequence of inhibiting 

 conditions. The stolons arising from the inhibited developmental 

 stages grow at the expense of other parts and in time the whole 

 substance of the inhibited larva may be used in the growth of the 

 stolon or stolons arising from it, leaving only the empty perisarc 

 in the position of the larval body and an empty perjsarcal tube 

 connecting this with the stolon. Fig. 27 shows a case in which an 

 inhibited form gave rise to a single stolon, which finally used up 

 the whole larval body in its growth. At the stage shown the tip 

 of the stolon had reached a point several centimeters distant from 

 its point of origin, only a small part of the perisarcal tube con- 

 necting stolon and larval body being shown in the figure. After 

 using the substance of the larval body, the stolon tip continues to 

 grow at the expense of its more basal levels. The cells of the tip 

 remain in good condition, while those of the basal end become 

 shrunken and transparent and undergo atrophy. In this way 

 the ccenosarc of the stolon becomes shorter and shorter until only 

 a small mass of tissue remains. 



Figure 29 shows a case in which an inhibited form gave rise to 

 two stolons near together. At the stage shown they have used 

 the whole larval body and then their own substance to such an 

 extent that they are entirely separate from each other, except for 



