No. 7.— CONTRIBUTIONS FROM THE ZOOLOGICAL LABORATORY 

 OF THE MUSEUM OF COMPARATIVE ZOOLOGY AT HARVARD 

 COLLEGE, UNDER THE DIRECTION OF E. L. MARK, No. 228. 



Effects of radium on living substance. — I. The influence of radia- 

 tions of radium upon the embryonic growth of the pomace-fly 

 Drosophila ampelophila, and upon the regeneration of 

 the hydroid Tubidaria crocea. 



By E. D. Congdon, 

 Introduction. 



These studies on the effects of radium, the first two. of which are 

 here pubhshed, were begun in 1906, at the suggestion of Professor 

 Mark. The work was carried on under liis direction in the Zoological 

 Laboratory at the Museum and in conference with Prof. Theodore 

 Lyman of the Jefferson Physical Laboratory. The results on other 

 parts of the work are reserved for further experimentation before 

 publication. 



Space does not permit here an extended description of the three 

 types of radiation given off by radium, the alpha, beta, and gamma 

 rays. According to the commonly accepted corpuscular theory of 

 matter, two of the three, the alpha and the beta, consist of particles 

 of matter. The third, the gamma rays, are movements of the ether. 

 The alpha rays are so little penetrating that a few sheets of paper 

 will absorb them; the beta rays, on the contrary, are more penetrat- 

 ing and may even traverse a considerable thickness of metal. The 

 gamma radiations exceed the beta rays, as well as X-rays, in their 

 penetrating power. The larger portion of the energy emitted by 

 unscreened radium is in the form of alpha rays. Further information 

 as to radium and its radiations may be found in such standard works 

 as Rutherford's Radioactivity and his Radioactive Transformations. 



In spite of the numerous investigations on the biological action 

 of the three types of radium rays which have appeared since the early 

 notices from Becquerel and others, not much progress has been made 

 in analyzing their action. This is evident from the fact that we 

 know almost nothing of their distinguishing biological effects other- 



