BERNARD L. STREHLER 375 



about 50 years. They are kept in a bell jar about 13 inches in dia- 

 meter and 9 inches in depth. The original specimens are all to- 

 gether on a piece of stone which bears a number of deep depressions 

 in which the anemones have ensconced themselves. These conditions 

 closely resemble those in which Sagartia troglodytes are usually 

 found, the specific name of this anemone being derived from its 

 favorite habit of dwelling in holes and crevices of the rocks. These 

 specimens have been under constant observation since 1862 and 

 there can be no doubt that they are the original ones." 



These animals were later transferred to the Edinburgh Zoo and 

 lived until 1942 when all of them were simultaneously found dead 

 one morning (7). I doubt that they died of "old age." 



It certainly seems well established that a process of clonal aging, 

 such as frequently occurs in protozoan cultures, is not a regular 

 process among coelenterates ( 20 ) . Lines of hydra in which the only 

 means of propagation was asexual budding have been kept for 

 decades without sexual crossing. In our own studies of Campamdaria 

 ftextiosa, a colonial hydroid, (30, 31), we have kept a clone growing 

 vigorously over the last three years on an artificial medium in the 

 laboratory without sexual crossing. This strain was obtained earlier 

 from Crowell (8, 9, 10) who had likewise kept it and perpetuated 

 it as a clone for a numlier of years. 



Although, in the opinion of most recent investigators, certain 

 Hydrozoa such as hydra and probably many species of Anthozoa 

 do not undergo individual aging, there are closely related species 

 such as Obelia commissumlis and Campamdaria flexuosa which 

 do undergo a clear and most remarkable aging process. The details 

 of the senescence and death of Campamdaria hydranths is currently 

 being investigated in our laboratory. The developmental history of 

 clones of this species is approximately as follows. The animal grows 

 by sending out a root-like structure called a stolon which grows 

 on a hospitable substratum, either rock, piling or, even in some 

 cases, an algal surface (e. g., Fuciis). At periodic intervals, upright 

 branches appear as shoots from the main stolonic growth. These 

 proceed upwards for a certain distance, acquire a series of annula- 

 tions, the most distal of which eventually enlarges into a bulblike 

 structure. This primitive structure then elongates, acquires a rhyth- 

 mic muscular contractility, lays down a protective covering shield 



