400 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



Bathkea stage (Hseckel). 

 Lizzia stage (Forbes). 



3. Perradial— 3333 

 Interradial— 3333 



5. Perradial— 3334 



Interradial— 3333 

 2. Perradial — 4444 



Interradial — 3333 



4. Perradial— 5443 

 Interradial — 3333 



1. Perradial — 5555 ? Margellmm gratmn, 

 Interradial— 3333 Hc^ckel. 



Sars states that the young medusa leaves its parent 

 with 1 interradial and 3 perradial tentacles. This stage I 

 did not meet with, but found the next stage with 2 inter- 

 radial tentacles. The interradial tentacles never exceed 

 three in each group, but the perradial tentacles increase 

 until five is reached, which is the maximum. Agassiz (i) 

 describes an American species Lizzia grata, {Margellium 

 gratum, H?eckel), which has five perradial and three 

 interradial tentacles in each group. These tentacles 

 develop in the following order. At first there is in each 

 perradial group one long median tentacle, and on each 

 side of it a small tentacle. Next, the median tentacle of 

 the interradial group appears, followed by a pair, one on 

 each side of it. At this stage the medusa has 3 tentacles 

 in all the groups. Finally the two remaining tentacles of 

 the perradial groups appear to complete the set of five. 

 Agassiz also describes the development of the oral ten- 

 tacles. In the young medusa there are four simple, 

 unbranched, oral tentacles terminating in a cluster of 

 nematocysts. Each tentacle branches near the extremity 

 and each branch terminates with a cluster of nematocysts. 

 Next the lateral clusters appear, one on each side of the 

 original tentacle. Then arises a cluster midway between 

 the bases of the four tentacles, and finally, a cluster 

 between the branches at the end of the tentacle. 



