322 ^- J- (^oldfarb 



from the apical region give rise to fezver polyps than the branches 

 from the middle and basal regions. While polyps at the apical 

 end of stems are common, they are rare on the apical ends of 

 branches.^ 



HETEROMORPHOSIS 



The phenomenon of heteromorphosis*' in hydroids, has been 

 investigated by Driesch, Loeb, Morgan, Stevens and others, par- 

 ticularly upon unbranched or slightly branched colonies. It was 

 hoped that experiments upon a much branched hydroid like 

 Eudendrium ramosum, v^^ould afford further insight concerning; 



1 The conditions underlying the formation of heteromorphic 

 polyps. 



2 The effects of such polyps upon the regeneration of other 

 polyps on the stems. 



3 The rate of development at different levels of the stem. 



4 The ccenosarc, its movements and its effects in the produc- 

 tion of heteromorphic polyps. 



A great many observations on large stems of all kinds had 

 show^n that polyps are rarely produced at the basal region, partic- 

 ularly at the basal cut ends, though common enough at middle 

 or d stal regions. Smaller stems or pieces of large stems — bear- 

 ing from 15 to 20 branches — regenerated more basal hydranths 

 than the much larger stems, though still less than the number 

 of apical polyps. 



Experiment ^^. Large stems with lateral branches removed were 

 cut into three nearly equal pieces. Further details are given in 

 Experiment 3. The number of hydranths regenerated at the oral 

 and the basal cut ends of each piece, two and five days after their 

 first appearance, are given in the following table: 



^See Gast and Godlewski, loc. cit. 



^The following papers on Heteromorphosis and Polarity give various hypotheses to account for these 

 phenomena in hydroids: Bickford '94 J.Mcrph.; Driesch '92 Biol. Cent., '96 Vierteljahrs-schr. Nat. 

 Ges. Zurich, '97 Archiv f. Ent., '99 Archiv f. Ent.; Loeb '91, Utber Heteromorphose, Wiirzburg; Mor- 

 gan '01 Biol. Bull., '01 Archiv f. Ent., '04, '05, '06 Journ. Exp. Zool.; Morgan and Stevens '04 Journ. 

 Exp. Zobl.; Stevens '02 Archiv f. Ent. 



