L.M.B.C. MEDUSA. 399 



has removed Lizzia octopunctata, Forbes, to the genus 

 Margellium. 



During May, 1893, I found in Port Erin Bay medusae 

 which belong undoubtedly to the same species as those 

 described by Forbes as Lizzia octopunctata. Some of the 

 specimens correspond exactly with the descriptions given 

 by Sars and Forbes, and others are without doubt other 

 stages, showing earlier and later forms, of the same 

 species. The oral tentacles of all the specimens taken 

 have four clusters of nematocysts. Each oral tentacle 

 bifurcates near its extremity and each branch terminates 

 with a cluster of nematocysts. The two other clusters 

 are on a short branch, one on each side of the main stem 

 of the tentacle. 



The umbrella of the smaller specimens is from 1 to 2 

 mm. in diameter, and of the larger specimens about 3 to 3^ 

 mm. in length and slightly less in width. The colour 

 of the tentacle-bulbs varies, being either yellowish brown, 

 dark brown, or black. The great difference in the speci- 

 mens is in the number of tentacles in each group, and it 

 is upon the number of tentacles that Haeckel mainly bases 

 his classification. Twenty specimens are sufficient to 

 show the change of number of the tentacles in each 

 group, and in the following list I have arranged 20 speci- 

 mens so as to show the increase in the number of tentacles 

 in each group. This increase is not a variation, but 

 simply shows stages in development. 



Numher of tentacles in 

 Number of specimens. each group. 



1. Perradial — 3333 Margellium stage (Haeckel). 



Interradial — 2222 Lizzia stage (Forbes). 



4. Perradial— 3333 

 Interradial— 3332 



3333 

 3233 



3333 

 3233 



3333 

 3233 



