128 STUDIES IN GENERAL PHYSIOLOGY 



4. I did not succeed in observing the polyps in the 

 process of taking up food. Yet I have noticed in both the 

 oral and the aboral polyps the same sudden closure of the 

 tentacles which occurs in Actinians when they seize their 

 food and swallow it. I shall show later in Actinians that 

 heads which have been newly formed in abnormal places 

 behave like normal heads in the matter of taking up food. 



IV. THE DISCREPANCY BETWEEN ALLMAN'S THEORY OF PO- 

 LARITY AND THE BEHAVIOR OF TUBULARIA MESEM- 

 BRYANTHEMUM 



1. I mentioned in the introduction that Allman based 

 his theory of polarity on observations made upon Tubularia. 

 The discrepancy between Allman's ideas and my observa- 

 tions compels me to enter into a more detailed discussion of 

 his theory. 



The passage in Allman 's treatise which is of interest to 

 us is the following: 



There is thus manifested in the formative force of the Tubu- 

 laria stem a well-marked polarity, which is rendered very apparent 

 if a segment be cut out from the center of the stem. In this case, 

 no matter in what position the segment may be, that end of it 

 which was directed downward or proximally, while it formed a 

 part of the unmutilated hydroid, will never develop a polypite, but 

 will extend itself as a simple prolongation of the coenosarc; while 

 the upper or distal end, instead of becoming simply elongated, will 

 shape itself into a true polypite; and all this is true, though of 

 course not the least difference in structure or form can be detected 

 between the two extremities at the time of section. 1 



Allman adds in a note that the observations of Daly ell, 

 who made numerous regeneration experiments upon Tubu- 

 laria indivisa, are in perfect accord with his own. By 

 reading Dalyell's paper one, indeed, finds the same idea 

 expressed as by Allman, although the term "polarity" is 

 not used. It might be thought that Tubularia indivisa, upon 



lLoc. cit. t pp. 392 ff. 



