94 C. M. Child 
a matter of fact, however, in almost all if not all observed cases the 
directive feature becomes less and less conspicuous in isolated 
pieces, with approach to one or both ends of the body, and with 
decrease in the size of the piece, while the regional differences 
become more conspicuous under these conditions. If. the direct- 
ive feature is the primary feature of polarity it seems strange that 
it should give place more or less completely to a regional feature 
under these conditions. 
Moreover, Lillie finds various evidences of the existence of a 
molar structure in the ground substance, which he regards as con- 
centric. It seems at least possible that such a structure may 
possess axial characteristics which have not yet been recognized. 
The apparent homogeneity of the ground substance is certainly no 
argument against the existence in it of a polar structure. In short, 
Lillie’s conclusions do not seem to follow necessarily from the 
facts and his argument is therefore somewhat unconvincing. 
Morgan does not seem to have presented in his recent paper? any 
more cogent reasons for acepting this hypothesis. In so com- 
plex a mixture of colloids and other substances as protoplasm 
certainly is, the possible morphogenic factors are so numerous and 
varied that we are scarcely justified in turning at once to the mole- 
cule when direct observation fails us. 
It seems to me that the hypothesis rests essentially on negative 
evidence, so far as the organism is concerned, i. e., in the absence of 
any visible basis for polarity it is assumed that the phenomena 
concerned are the result of molecular orientation. The phenom- 
ena of fluid crystals are undoubtedly of great interest, but it is by 
no means certain that there is anything more than a very remote 
analogy between them and the phenomena underlying organic 
polarity and symmetry. Such an assumption seems to neglect the 
fact that protoplasm is not a homogeneous chemical substance nor 
even a simple mixture. Moreover, it exists in cells and within the 
cells various localized differentiations may occur which may well 
be the result of a molarstructureof the ground substance. Besides 
all this restitution may occur in isolated pieces after centrifuging. 
? Biol. Bull., xvi, 5, 1909. 
