242 



MEDUS/E OF THE WORLD. 



Rhode Island; and it is probable that several species are represented in the collection. The 

 following is a summary of the principal results: Among 3,917 specimens, 9 had 3 radial- 

 canals, 20 had 5, and 3 had 6 canals. In 14 specimens one of the radial-canals forked. 3,871 

 had 4 radial-canals. In other words, 98.8 per cent had 4 canals, 0.51 per cent had 5, 0.22 

 per cent had 3, 0.076 per cent had 6 canals, and 0.35 per cent had forked canals. It is 

 remarkable that there were no variations in the lips, these being 4 in number in every 

 specimen examined. On the other hand, the tentacles were very variable in number, and in 

 14 specimens they were forked or gave rise to basal spurs resembling those of Laodicea, etc. 

 The egg or sperm seemed to develop to maturity with normal frequency even in abnormal 

 specimens with 3, 5, or 6 canals. They also found that in Obelia the tendency to produce 

 medusae with 5 radial-canals is about twice as great as that to give rise to individuals with 3 



General Characters of the So-called Species oj Obelia — Continued. 



*Probably a variety of O. geniculata with toothed margins to the hydrotheca'. 

 j-Probably identical with 0. plana. 



