DIFFERENTIATION IN HYDROID COLONIES. 



147 



Table VI. 



Measurements in Degrees of Angle. 



The lengths of the hydrothecse, taken through the mesial 

 tooth, are recorded in Table VII, There is a definite tendency 

 to increase in length toward the distal end of each hydrocladium, 

 the longest hydrotheca, however, being subterminal. 



Table VIL 



Measurements in mm. X 95- 



In Table VIII., the widths of the hydrothecse previously used 

 have been taken along the line defining the obliqueness of the 

 opening of the hydrothecse. As the figures show, this character 

 is too variable to be very useful to the experimeter. Neverthe- 

 less, in common with the characters considered in the three tables 



