LIFE-HISTORY OF CRASPEDACUSTA RYDERI. 4,V) 



the eye. The only method of distinguishing them is by an 

 examination of the gonads. 



DISTRIBUTION. 



In my former paper I stated my belief that Microliydra and 

 Craspedacusta were merely hydroid and medusa stages of one 

 and the same species, namely Craspedacusta ryderi. I also 

 stated that I believed the hydroid much more widely distributed 

 than formerly thought, and that it was only when conditions 

 were favorable that the medusae appeared. My further studies 

 have strengthened this point of view. No medusae appeared in 

 Boss Lake in 1924 and 1925. I know the hydroids were present 

 in 1924. No medusae were present in Benson Creek in 1925. 

 Yet I found the hydroids. 



The fact that both males and females occur in the Kentucky 

 River may indicate that this is their point of origin from a 

 marine life. During the elevation of this region, which at times 

 has been a part of the sea, it is possible that Craspedacusta 

 became cut off from the main sea and that it was able to adjust 

 itself in the slow change from salt to fresh water. 



SIZE. 



The first medusae taken in Boss Lake, September 1919, were 

 large, measuring from one half to three fourths of an inch in 

 diameter. They were perfect specimens. In later summers they 

 were never so large nor so perfect. I attributed this change to 

 the presence and destructive action of many amoebae. The 

 medusae taken in the Kentucky River were large and perfect, 

 similar to the first specimens taken in Boss Lake. I did find 

 amoebae on them, however, when they were allowed to live in 

 the laboratory until they showed signs of disintegration. 



SYSTEMATIC POSITION. 



The systematic position of Craspedacusta has been a debatable 

 one. This is not surprising, however, when we look at the 

 taxonomic work on the Hydromedusae. A glance at the literature 

 tells one that classification in many cases has been attempted 

 without knowing much or anything of the life history. Hydroids 

 have been classified independently of medusae and medusae 



