PLATE 4. 



Fig. i. Sarsta mirabilts. Abnormal medusa with a tentacle arising from 

 the side of the manubrium. Nahant, Massachusetts, May 8, 

 1897. Metschnikoff, 1870, observed a similar abnormality in 

 Slabbena catenata. 



Fig. 2. Median section of a young medusa of Sarsia mirabilis. The ocellus 

 on the right-hand tentacle is shown as if depigmented in order to 

 illustrate its structure. The eye on the left-hand tentacle-bulb is 

 shown normally pigmented. 



Figs. 3 and 4. Sarsia mirabilis var. reticulata, young medusa. Figure 4, 

 one of the nematocyst-cells from the tentacles of figure 3. Agas- 

 siz Laboratory, Newport, Rhode Island, June 13, 1895. 



Drawn from nature, by the author. 



