I r. 



SCIENCE. 



[N. S. Vol. XX. No. 518. 



advisable. Tendency to make these technical 



and it might be wise to encourage this idea. 



Xet affiliated societies here take the leading 



"position. 



Ji. P. Felt (15 April, '04, No. 485, pp. 622- 



623). 



-Two general sessions of association ought 

 'to meet every demand at the meetings; one 

 to mark the opening of the meeting, the 

 other to give the president opportunity to de- 

 liver his address. Notices for each day could 

 appear on program, thus allowing unbroken 

 day. Morning meetings devoted to general 

 papers. Afternoon meetings to special papers 

 before subsections or societies. Evenings to 

 sessions of members for short addresses on 

 topics of general interest. We would favor 

 the continuing of the complimentary lecture 

 to the people of the city where the meeting 

 is held. All evening meetings should close by 

 9 :30, leaving time for banquets, etc. 

 W. J. Seal (20 Mch., '04, No. 490, pp. 797- 



798). 



" Let association keep up all its sections, 

 possibly adding to the number, freely cooper- 

 ating with special societies, each section 

 showing a willingness to unite in preparing a 

 program with any one or more special societies 

 having a like object." Years ago Professor 

 Cope, Mr. W. A. Eogers and Mr. E. S. Morse 

 objected to presentation of popular papers. I 

 have recently thought it desirable to have a 

 number of selected speakers present some topic 

 or series of topics in a popular way to attract 

 ' outsiders.' 



3. " Education, economics, but not philol- 

 ogy." 



4. " Once a year, preferably in winter, till 

 this date has had a fair trial." 



5. " Meet most of time in populous regions 

 from Washington to Boston, Detroit to Chi- 

 cago, where many people are most sure to 

 attend." 



AN ANALYSIS OF THE PHENOMENA OF 

 ORGANIC 'POLARITY.'* 



The so-called 'polarity' that is shown in 



the regeneration of animals and plants has 



* Read before the National Academy of Science, 

 asrovember 16, 1904. 



always been regarded as an expression of 

 a fundamental infliience of the old upon 

 the new growth. By polarity is meant in 

 a general way that from the anterior end 

 of a piece of an animal a new head regen- 

 erates, and from the posterior end a new 

 tail. Many exceptions to this rule have 

 been discovered in recent years, and in the 

 light of these discoveries, I think, we are 

 now in a position to undertake a more thor- 

 ough analysis of the phenomena of organic 

 polarity than was possible without these 

 new facts to guide us. 



I shall group the main points to be dis- 

 cussed under four artificial headings : (1) 

 'Regeneration when no Alternative Exists 

 at a cut Surface,' (2) 'Regeneration when 

 an Alternative does Exist,' (3) 'Regenera- 

 tion when the Relative Rate of Growth De- 

 pends on Preformed Elements (Buds) ' 

 and (4) ' Lateral Regeneration. ' 



1. REGENERATION WHEN NO ALTERNATIVE 

 EXISTS AT A CUT SURFACE. 



If the tail of a tadpole is cut off a new 

 tail regenerates at the posterior end of the 

 tadpole. The tail that is cut off does not 

 ordinarily regenerate at its anterior end, 

 because it dies before regeneration can 

 take place. If it is kept alive, either by 

 grafting or by remaining partially at- 

 tached, it regenerates from its anterior end, 

 not a tadpole, but another tail, reversed in 

 direction. The conditions are such that 

 both at the anterior and at the posterior 

 cut surfaces only a tail can develop. The 

 new tail from the posterior cut surface is 

 in the direction of the old polarity, while 

 that from the anterior cut surface is in a 

 reverse direction. 



In the earthworm a similar condition has 

 been found. If the worm is cut in two 

 at any level behind the gizzard, both cut 

 ends regenerate a tail. Anterior to this 

 level, however, the posterior piece regen- 

 erates a head on its anterior end. It is 



