POLARITY AND BILATERALITY OF THE ANNELID EGG. // 



Morgan has made the suggestion (Science, August 28, 1908, 

 p. 288) that formative substances other than the visible granules 

 here referred to may possibly be present in the sea urchin's egg, 

 and that such materials are not seriously disturbed by a cen- 

 trifugal force sufficient to separate the visible substances of the 

 egg ; but that if these more fundamental substances are displaced, 

 interference with the normal development would be expected. 

 According to this conception vital organization would still be a 

 function of equilibrium and interaction of diverse substances. 

 The logical possibility of such a conception must be admitted, 

 but it avoids none of the difficulties inherent in the usual 

 hypothesis of organization, and seems to me to offer no possi- 

 bility for explaining the polarity or bilaterality of parts of an 

 ovum or "the phenomena of regulation in general. 



The existence of polarity and bilaterality in an optically 

 homogeneous medium, and the persistence of both as to orienta- 

 tion under experimental conditions that seriously modify the 

 quantitative relations of the oriented medium in different regions 

 (as, for instance, when the yolk granules are packed closely into 

 the small cell of the two-celled stage of Chatopterus) seem to me 

 to argue for a molecular basis of the fundamental principle of vital 

 organization. 



Lehmann's observations on fluid crystals offer interesting 

 analogies that are suggestive in the consideration of such funda- 

 mental biological problems. They show that the conception of 

 crystallization as applied to vital organization does not meet 

 with some of the difficulties formerly considered inherent in the 

 analogy. Particularly his observations on the so-called myelin 

 forms where innumerable fluid crystals determine the form and 

 behavior of a single aggregate, suggest most interesting biologi- 

 cal analogies, and aid to a certain extent in conceiving a doubly 

 heteropolar condition of aggregation such as is presented by the 

 animal egg. 1 



1 It is not of course the author's intention in this communication to attempt to 

 establish the validity of the analogy, but only to point out its possible application to 

 the demonstrated organization of the ground substance of the cytoplasm. A good 

 discussion of the entire analogy of crystallization to morphogenesis is contained in 

 Przibram's article " Kristall-Analogien zur Entwicklungsmechanik der Organismen," 

 Archivfur Entw'mech., Rd. XXII., 1906. 



