188 ON THE PELAGIC FAUNA OF PLYMOUTH FOR SEPTEMBER, 1897. 



October and placed in an aquarium. In three days it liberated not 

 less than 4450 medusae, and when the colony was preserved there was 

 still left a good stock of young medusa buds upon the branches. (See 

 page 189.) 



NOTES ON MEDUSAE. (September, 1897.) 



Olclia lucifera. — This was by far the most abundant medusa during 

 September. On some days thousands were taken in the tow-nets. 



Phialidium luslciamtm. — Specimens of this species were nearly always 

 present, from the earliest to the adult stage. 



Phialidium cyiiibaloideum. — Most of the specimens belonged to the 

 earliest stage, with four tentacles ; a few belonged to the second 

 stage, with eight tentacles. The adult was not taken. 



Lar sahellarum. — The earlier and intermediate stages were usually 

 taken. The adult form was very scarce. 



Amphinema dinema. — Nearly all belonged to early stages. 



Cyiccandra areolata. — Only the intermediate stages present. (For 

 description and figures of this species see Proc. Zool. Soc, part iv., 

 1897.) 



Lizzia hlondina. — This medusa begins its free-swimming existence with 

 four single perradial tentacles and four single interradial tentacles, 

 and as it grows the perradial tentacles only increase in number 

 until there are three tentacles in each of the perradial groups. 

 The early stages have been described as distinct species, and are 

 recorded in Haeckel's System der Medusen under the following 

 names : — 



First stage : Eight single tentacles = Dysmorphosa minima. 

 Second stage : Four perradial groups with two tentacles and four 



single interradial tentacles = Lizzia clajparedei. 

 Third stage : Four perradial groups with three tentacles and four 

 single interradial tentacles = Lizzia hlondina. 



In the first and second stages the medusa usually buds off medusae 

 from the wall of the stomach, and in the third stage the generative cells 

 make their appearance. The first and second stages have also been 

 described with ripe generative cells, and consequently regarded as adult 

 medusae and distinct species. 



During my visit to Plymouth in 1895, and also at Port Erin and 

 Valencia Island, I have always taken the first and second stages with 

 medusa-buds and the third stage with generative cells. This year 

 at Plymouth I obtained specimens of the first and second stages in 

 the same tow-netting, some with medusa-buds and others with genera- 



