142 



H. B. TORREY. 



Table I. 



Measurements in Degrees of Angle. 



Table II. 



I 



I 



Table III. 



Measurements in mm. X 95- 



The facts formulated above concern the differentiation of inter- 

 nodes of single hydrocladia from various regions of the colony. 

 On further examination, Tables I. and III. suggest that the 

 character under consideration tends to decline from its maximum 

 less rapidly on hydrocladia in the middle region of the colony 

 than on hydrocladia either proximal or distal to them. This 

 suggestion that the colony may have a typical form, exhibiting a 

 differentiation from base to tip, analogous to what is so familiar in 

 the leaves of plants, is supported by series of measurements at 

 the tips of several colonies. One such series is presented in 

 Table IV., in which are given both the length of each theca, 

 through the unpaired or mesial tooth (upper figures), and the 

 width, of the theca through the tip of the mesial nematophore 

 (lower figures in italics), as in Table III. 



