46 



ME. P. H. CAEPENTER ON THE GENUS ACTmOlMETEA. 



Table II. — Showing Irregularities in the Position of the first Syzvgium, 



In nearly every case the irregularity appears to have heen the result of regeneration, 

 the arm having been broken, cither in the distichal or in the palmar series, or between 

 tlie third brachial and the preceding axillary, and a new one developed with an irregular 

 syzygial series ; although in many cases similarly regenerated arms of other specimens 

 exhibit perfectly normal series of syzygia. One of these unusual cases, in which there is 

 no syzygium on the third brachial (6;,) and the first syzygium occurs on the tenth seg- 

 ment (i,„)j ■which is usually the ])osition of the second syzygium, is seen in PI. II. fig. 8. 



We have seen that wlicn the first syzygium is on the third brachial, the position of the 

 second is in the great majority of cases on the tenth l)rachial ; that is to say, the first 

 syzygial interval is six simple segments, wliile the second and all the subsequent intervals 

 are, as a general rule, only three simple segments, though the range of variation on either 

 side of this number is very great. 



Table III. shows the variations in the positions of the second and third syzygia in all 

 those 283 arms in which the iirst syzygium is on the third brachial. Erom the last 

 column of tliis Table it is evident that in Acl. pohjmorpha and its varieties the normal 

 position of the second syzygium is on the tenth brachial, and that in those cases in 

 which it does not occupy this position it is much oftener on the eleventh or twelfth 

 segment than on the eighth and ninth ; i. e. that variation, when it occurs, is in the direc- 

 tion of increase rather than of decrease in the length of the first interval. This is more 

 clearly seen in Table IV., which shows the number of segments intervening between the 

 first and second syzygia in all the above cases. 



