ADVENTITIOUS REPRODUCTION IN HARENACTIS. 9 



from the figure that in two cases the tentacles which apparently 

 arise directly upon the line of union are forked at their tips: this 

 means that they began their development as two separate ten- 

 tacles, one on each side of the line of union, and later united to 

 form a single tentacle. Similar conditions are shown in Fig. 8, b, 

 and in Fig. 10 of my earlier paper ('096). 



CONCLUSION. 



As regards the interpretation of these peculiar structures, there 

 is little to add except by way of confirmation to the conclusions 

 of my preceding paper on the subject. The outgrowths on the 

 rings unquestionably represent a kind of reproduction which 

 results from a certain degree of physiological isolation of parts, 

 in other words from the decrease in physiological correlation, 

 which is itself the result of the removal of important elements 

 of the original organization and of the union of the oral with 

 the aboral end. Moreover, it seems evident that the localization 

 of the tentacle groups along the line of union is due to "chance" 

 factors, probably in part to differences in the amount and rapidity 

 of the growth of new tissues and on the other hand to differences 

 in the degree of injury to the old organization. 



That the new polarities have no direct relation to the original 

 polarity is evident from the fact that they may arise from either 

 the oral or the aboral side of the line of union, or from both sides. 

 From these facts we must conclude that they are the result of 

 local conditions in the regions concerned, and of conditions 

 which are not primarily concerned with the original organization. 



As regards symmetry, the new growth may be either bilaterally 

 or radially symmetrical or asymmetrical. Clearly the symmetry, 

 as well as the polarity, has nothing to do with the original 

 organization. 



And finally, these regulatory phenomena cannot be satisfac- 

 torily interpreted by the hypothesis which regards polarity and 

 symmetry as essentially a summation of the polarities and sym- 

 metries of ultimate oriented particles or molecules. How, for 

 example, shall we account on the basis of this hypothesis for 

 the appearance of bilaterally symmetrical groups of tentacles in 

 an organism which is naturally radially symmetrical. Further- 



