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 cf 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.! 
Allman adds in a note that the observations of Dalyell, 
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 
1Loce. cit., pp. 392 ff. 
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