Physiological Morphology 



95 



are exhibited by the same animal. If we cut out a sufficiently 

 large piece of the stem of Tubularia mesemhryantheinum , and 

 place it in the bottom of a dish of water, 

 carefully protected from jarring, the ante- 

 rior end of the piece gives rise to a new 

 polyp, the posterior end to a root; but if 

 we hang up the stem in such a way that the 

 posterior end does not touch the surface of 

 the glass, and is sufficiently provided with 

 oxygen, this end, too, produces a pol}^:), and 

 we have a true case of heteromorphosis 

 (Fig. 32). In all cases the polyp at the oral 

 end is formed first, and a relatively long 

 time (one or more weeks) elapses before 

 the aboral polyp is formed. Under one con- 

 dition, however, I could cause the stem to 

 form a polyp at the aboral as quickly as at 

 the oral end, namely, by inhibiting or re- 

 tarding the formation of the oral polyp. 

 This could be done readily by diminishing 

 the supply of oxygen at the oral end. In 

 such cases the aboral polyps were produced 

 almost as quickly as the oral pol^'ps.^ 



Ki< 



32. 



III. THE MECHANICS OF GROWTH IN 

 ANIMALS 



In order to arrive at an explanation 

 of the phenomena of organization we must 

 ask w^hat the physical forces are that 

 determine the formation of a new organ. 

 We know that the ultimate sources of 

 energy for all the functions of living bodies 



n«'toro- 



inorphosis in TuKuta- 

 ria. From uaturr. 

 Thcnormal Tittntlunn 

 (Muls at oin' mil In a 

 stolon, at tlu> olIuT 

 in a IuukI or |K)lyp. 

 If a pitfi' (1 f> Is rut 

 out and susprndt'*! in 

 watiT a nrw ' " r 

 polj pi-aml/i- 1 



at lM)th inds. U r 

 ran thus product- an 

 animal whirii t«Tnil- 

 nat«'s in a head at 

 innh t-ndsof it,s iHKly; 

 wliilf in Vln. 2H an 

 animal was n-pn-smt- 

 r<l whirh «*nd«.'<l at 

 l>oth rnds in a stolon 

 or fiK)t. 



1 It was found later independently by lx)Mi Clodlowski and myself that If wo 

 ligature the stem of a Tubularian the polyps at both ends are fornietl slmultam*- 

 ously (1912). 



