March 20, 1908] 



SCIENCE 



447 



the mandibles. At the moult from the 

 nauplius into the metanauplius we find in 

 addition two pairs of maxillae, often two 

 pairs of maxillipeds, and sometimes one or 

 more pairs of swimming legs. To which 

 of the three nauplius appendages should 

 preference be given, and if the mouth- 

 parts be chosen as a basis of classification 

 which of them possesses the greater value? 



Degeneration quietly eliminates these ap- 

 pendages one by one; why may not its 

 testimony be taken when the case is so 

 difficult of decision otherwise? 



Again development requires that we ob- 

 tain the eggs and rear the young through 

 successive stages; any one who has tried 

 this on the eopepods realizes how very 

 difficult it is. And even when accom- 

 plished, many of the conditions are of 

 necessity abliormal, and in consequence 

 might produce abnormal results. 



Degeneration, on the other hand, is pro- 

 duced upon the adults in their native 

 habitat and surrounded by their usual 

 conditions. We can obtain and study the 

 results with comparative ease; we are not 

 obliged to reproduce any of the conditions. 



Degeneration thus determines in the 

 eopepods which of the appendages are the 

 most stable and the least susceptible to 

 change ; it selects the first antennse from 

 among the nauplius appendages and of the 

 mouth-parts the mandibles as the most 

 stable and the first maxillse as the least so. 

 Consequently that classification is the best 

 which is the most fully based on these 

 stable elements. We find such an one 

 originally proposed by Thorell in 1861, cor- 

 rected by Glaus in 1862, by Gerstaecker in 

 1881, and finally by Canu in 1892. 



Wound-reparation and Polarity in Ten- 

 tacles of Actinians: Herbert W. Rand, 

 Harvard University. 

 At the Bermuda Biological Station for 



Research, in the summer of 1907, I studied 



the reactions resulting from cutting the 

 tentacles of certain large actinians {Con- 

 dylactis and Aiptasia). If a piece of ten- 

 tacle is removed by a transverse cut, within 

 a few minutes the open cut end of the 

 stump is closed by a concentric inbending 

 of the wall of the tentacle. The newly 

 closed end is hemispherical except for the 

 presence of a small cylindrical nipple-like 

 projection at its center. This closure is 

 effected by contraction of the circular 

 muscle fibers. The "nipple" results from 

 extreme contraction of the circular fibers 

 immediately proximad of the plane of 

 cutting. Within a day or two after the 

 cutting there ensues a rearrangement of 

 the elements of the tissues in the vicinity 

 of the cut, whereby results a permanent 

 closure which is not dependent upon mus- 

 cular contraction. Thus, the reparation 

 of the wound exhibits two phases. A 

 temporary repair is effected by active 

 muscular contraction pending the slower 

 reorganization of the tissues by which the 

 muscular tension at the cut end is relieved 

 and a permanent repair established. 



The closing of a distal cut end and the 

 formation of a "nipple" in the manner 

 described above take place in a tentacle 

 after it has been severed from the column. 

 This fact can not be interpreted as indi- 

 cating autonomy of fragments of the or- 

 ganism. The piece of tentacle is a frag- 

 ment of the actinian, but it is not a frag- 

 ment of the actinian organization because 

 in it are embodied the essential features of 

 the entire organization. 



When an excised tentacle is cut trans- 

 versely into several pieces, each piece shows 

 a definite polarity in that its two ends as- 

 sume distinctly different forms. Thus, in 

 any transverse zone of the tentacle two 

 modes of response to transverse cutting are 

 potentially present. In the event of 

 transection either one or the other mode 



