280 Proceedings of the Royal Physical Society. 



Sperm- sac surmounted witli large thread- ) 



cells, and forming the peduncle of a f Coryne gra- 

 fixed medusoid with differentiated f vata. 

 subumbrella and umbrella, . . j 



-»■ o , n j ■] -i •,•> ( Medusa of 



Imperfect free medusa ; peduncle witn ^ Coryne de- 



f Umbrella dif- 

 i ferentiated. 



/ Peduncle or 



tubular mouth, and united with a 

 single-cavitied generative sac 



cipiens, 

 Sarsia. 



alimentary- 

 polyp and ge - 

 nerative sac 

 not differen- 

 tiated from 

 each other 

 (see post). 



Perfect free Medusa of low type ; pe- 

 duncle four-tentacled or lipped, and 

 containing eight generative sacs coa- 

 lescing into four, which are situated 

 alternately with the tentacles or lips, 



Perfect free Medusa of low type; pe- 

 duncle four-lipped or tentacled, with 

 eight distinct generative sacs, one 

 placed on the side of each lip, 



Perfect free Medusa of higher type ; 

 peduncle four-lipped or tentacled ; 

 eight generative sacs, one on each 

 side of lateral canals, . 



ea 



Britannica, 

 the Medusa 

 of Atractylis 

 ramosa (fe- 

 male). 



Turris neglec- 

 ta, the Me- 

 dusa of Cla- 

 vula Gossii 



. (female). 



Oceania epi- 

 scopalis, 



Medusa of 

 Laomedea 

 geniculata. 



Medusa of highest type, with 4-6 lips "j Stomobra- 

 and 8-12 lateral canals, each canal > chium octo- 

 carrying a single generative sac, . ) costatum. 



Generative 

 sacs differen 

 tiated from 

 alimentary 

 polyp, but si- 

 tuated on it. 



Peduncle and 

 generative 

 sacs differen 

 tiated. Ali- 

 mentary po- 

 lyp taking no 

 part in re- 

 V production. 



/ Generative 

 I sacs on sepa- 

 I rate canals ; 

 two canals 

 correspond- 

 ing to each 

 lip. 



Of the generation of Stomobrachium we know nothing. 

 Claparede has shown that gymnophthalmatous Medusae may 

 produce Medusae without the intervention of the polypoid 

 phase ; but it is impossible to draw any line of distinction 

 between a Medusa and the medusoid phase of the Hydroid 

 polyp. Tuhularia indivisa produces its young as perfect 

 polyps without the intervention of the planuloid phase, Clava 

 with the intervention of that phase. In the life-history of 



