General Discussion 253 



He relates the ageing of the clone to interference with the normal 

 division of the micronucleus ; once that starts to go wrong the strain 

 dies out. 



Dempsey: I think there are some species of invertebrates which 

 reproduce parthogenetically and in which sexual stages never have 

 been observed. 



Villee : And I think too that it has been possible to culture clones 

 of unicellular animals for years and years without the least sign of 

 senescent degeneration; the ones in the culture after 10 or 15 years 

 were, in all respects, as good as the ones with which the experiment 

 began. 



Amoroso : After three days of the most pleasant deliberations this 

 symposium has reached the stage where the privilege of being 

 chairman becomes least acceptable, since I must now attempt a 

 summing up and endeavour to bring into relief the main points of 

 agreement and disagreement that have emerged during our dis- 

 cussions. In doing so, I shall indicate to you to what extent my 

 education on the ageing of transient tissues has been improved and 

 to what extent hiatuses still remain which must needs be filled. 

 If, therefore, any part of this summary fails in its allusion to major 

 points whilst emphasizing minor ones unduly, please ascribe this 

 not to any discourtesy but rather to my own limitations. 



I shall first take advantage of having the last word by defending 

 myself in respect to not providing a definition of ageing in my 

 opening remarks. To anyone who has listened to our several dis- 

 cussions, it must now be apparent why a straightforward statement 

 was not forthcoming. In our deliberations we have probably used 

 the word "ageing" in every one of its accepted connotations, yet 

 we have, none of us, succeeded in formulating a simple definition 

 to cover all the facts. 



Having thus defended my own rear, I pass on to summarize the 

 contributions. 



One category of evidence was presented by Dr. Price, Professor 

 Jost and by Professor Tuchmann-Duplessis. Dr. Price appropriately 

 opened with an account of the influence of the testes on the differen- 

 tiation of the Wolffian and Miillerian ducts and if anyone doubted that 

 the integrity of the Wolffian ducts, in genetic males, depended on testi- 

 cular function and that the Miillerian ducts were not thus controlled, 

 I hope that his doubts were set at rest. That Dr. Price did not con- 

 sider the effects of ovariectomy in genetic females is, however, to be 

 regretted, since such procedures might well have provided informa- 

 tion on the much disputed question of the manner of growth of the 



