418 HARPER— ORGANIZATION, REPRODUCTION 



interior cells are still actively swarming. The appearance here is as 

 if the development of the colony had proceeded normally until the 

 peripheral cells had gotten their places and then for some reason 

 activity was checked before the interrelations of the cells in the 

 interior had been worked out. It would be possible to express all 

 this confusion in degrees of displacement of the major axis of each 

 cell, but the situation is sufficiently clear from a comparison of this 

 colony with that shown in Fig. 4 without giving it such a mathe- 

 matical expression. I shall include data on this point in a later 

 study from a wider comparative viewpoint involving the general 

 effect of increasing numbers of cells on the organization of the 

 colonies. 



An extreme of irregularity of the second type which is ex- 

 pressed in the general contour of the colony is shown, as noted 

 above, in Fig. 26. Here the colony is crescentic in outline. The 

 type arrangement of cells for a sixteen-celled colony has entirely 

 disappeared and we can no longer recognize a central cell with two 

 concentric series about it and yet the inherited form of the cells is 

 quite perfectly developed in all cases. The modifications are such 

 as are obviously due to the special pressure relations under which 

 each cell finds itself. It is possible, of course, in many cases to 

 identify all the angles of any particular cell and to combine them 

 in homologous groups for the colony and a whole series of colonies, 

 as I have done for the series of more regular individuals. But in 

 these irregular colonies the major axes of the colony are frequently 

 quite unrecognizable and any particular included angle of a cell will 

 be so obviously misplaced and with such unusual pressure relations 

 that the comparison of its values in different colonies becomes a 

 very complex problem. 



I have brought together in Table VII. the values of all the in- 

 cluded angles in a series of both regular and irregular sixteen-celled 

 specimens of P. Boryanum. The values are given for groups dif- 

 fering by three degrees. The data could, of course, be represented 

 graphically in a curve, but the main point illustrated is brought out 

 quite well from a glance at the figures. They form a series culmi- 

 nating in 120° and ranging somewhat similarly above and below 

 this number. The total number of angles with greater value than 



