VAEIATION OF TENTACULOOYSTS OF AURELIA AURITA. 247 



comparing it with the first table it will be seen that the 

 percentage of abnormal specimens is nearly the same. In 

 the first set 22'6 per cent., and in the second set 20'9 per 

 cent, of the ephyrae are abnormal. 



The decrease is mainly due to a falling off in the number 

 of specimens with twelve tentaculocysts amounting to 2J per 

 cent. 



By taking a larger number of specimens the range of varia- 

 tion has extended from five to fourteen tentaculocysts, but 

 only one specimen of each of the two extremes has been found. 



The ephyra with five tentaculocysts (fig. 1) has four perra- 

 dial arms, equal in size; but the fifth is interradial and about 

 half the size of the other arms. 



The variation in the number of tentaculocysts does not 

 affect the other organs of the body, which may vary inde- 

 pendently of one another. 



Two specimens have only three bundles of gastric filaments 

 instead of the normal four; both have four mouth lappets; 

 but one (fig. 2) of them has six and the other seven tenta- 

 culocysts. Six specimens have six bundles of gastric filaments . 

 and six mouth lappets; three possess eleven tentaculocysts 

 (fig. 3) and the others have twelve. 



A few curious abnormal growths of the arms were also 

 observed. One specimen (fig. 4) has a perfect double arm 

 with two tentaculocysts, like two arms united together. 

 Another specimen (fig. 5) shows a bifurcation of an arm, each 

 branch terminating with a tentaculocyst. 



Perhaps the most interesting monstrosity is that which 

 occurs in a specimen (figs. 6 and 7) with a large outgrowth 

 on the aboral side of the umbrella. The outgrowth has two 

 arms, and one of them bears a tentaculocyst. There are also 

 seven other arms, with tentaculocysts, in the normal position 

 and a vacant place for two more. 



Adult Aurelia. 

 The adult specimens of Aurelia were also collected at 

 Plymouth during the summer of 1894, and belong to the 



