494 C. M. Child 



fact It so happens that approximately the maximum lengths appear 

 in these series either at fourteen or twenty-six days, thus making 

 it unnecessary to give in the table the measurements of intervening 

 or immediately following dates. In other words, the tentacles 

 in Series I reach their maximum length fourteen days after sec- 

 tion and are considerably reduced at twenty-six days. In the 

 other series the maximum is reached somewhere between fourteen 

 and twenty-six days, but reduction of the tentacles does not begin 

 until later. In Series II the maximum length is almost attained 

 at fourteen days, in Series III the tentacles are scarcely more than 

 half their maximum length after fourteen days, in Series IV al- 

 most the whole growth of the tentacles occurs after fourteen days 

 and in Series V the tentacles do not appear within fourteen days 

 (as a matter of fact, not until nineteen or twenty days) and soon 

 cease to grow. 



Series I to III show very clearly that the rapidity of growth of 

 the tentacles decreases with increasing distance from the oral end, 

 i.e., the tentacles not only require a longer time for the first stages 

 of differentiation, but after their differentiation grow more slowly. 

 In Series I a growth of 20-25 mm. occurs within fourteen days, in 

 Series II 10-15 mm. and in Series III 5-10 mm. in the same time. 

 The time of first appearance of the tentacles in these three series 

 differed by only about two days, yet the difference in the amount 

 of growth after fourteen days is considerable; in Series IV and V, 

 however, the rate of growth after the tentacles appear does not 

 differ very greatly from that of Series III: in Series IV the ten- 

 tacles appeared after about twelve days and grew 10 mm. in the next 

 fourteen days, and in Series V they appeared after about nineteen 

 days and grew 5 mm. in the next seven days. These pieces from 

 the aboral region of the body are always very irregular in time : in 

 some other series the rapidity of growth in such pieces is less than 

 half that in pieces like Series III. However, all the data which I 

 have obtained on the subject indicate that there is a marked dif- 

 ference in the rapidity of growth between distal and proximal 

 regions, and that such difference is independent of gross anatomi- 

 cal features in the different regions. 



The table shows that after twentj-'six days the difference in the 



