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BROOKLYN BOTANIC GARDEN MEMOIRS 



('13) has obtained in his very interesting and suggestive experiment » 

 with paraffine wax cooling over mercury, a configuration determined 

 entirely by the molecular forces operating in the system. It would 

 be possible to form a sphere out of these nineteen units, but there is 

 nothing in their number to favor the change from the discoid to the 

 spherical grouping. To make a hollow or solid sphere out of such a 

 group would involve very fundamental rearrangements. 



On the other hand, if we make a diagram of the arrangement of 

 the sixteen cells produced by binary fission, assuming for the sake of 

 simplicity that each pair of daughter cells instead of remaining flattened 

 upon each other with the resulting lateral displacement (Klein, Taf. 

 VI, Figs. 61-63) rounds up completely after the third division and 

 that the four cells first formed remain fixed by adhesion, we get the 



3 4 



Figs. 3 and 4. For explanation see text. 



configuration shown in text-figure 3. Here it is obvious that as con- 

 trasted with the arrangement in text-figure 4 it is a simple matter for 

 the group to become cup-shaped and spherical simply by folding in 

 the radial series and that the four outermost cells will come together 

 in a group of four with its members alternating with those of the 

 original group of four. 



The group produced by binary fission in two planes with elongation 

 of the cells upon their free surfaces and strong adhesion tends naturally, 

 especially in the cavity of a spherical mother cell, to produce a globular 

 young colony at the sixteen-celled stage. 



As noted, all authors agree in maintaining that all the cells of the 

 colony divide up to the sixteen-cell stage when the spherical form is 

 practically complete. The later stages have not been followed. 



