280 Proceedings of the Boyal Physical Society. 
Sperm- sac surmounted with large thread- 
cells, and forming the peduncle of a 
fixed medusoid with differentiated 
subumbrella and umbrella, 
Imperfect free medusa; peduncle with 
tubular mouth, and united with a 
single-cavitied generative sac 
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, . 
Medusa of highest type, with 4-6 lips 
and 8-12 lateral canals, each canal 
carrying a single generative sac, . 
Coryne gra- 
vata. 
Medusa of 
Coryne de- 
cipiens, 
Sarsia. 
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. 
Stomohra- 
chium octo- 
costatum. 
Umbrella dif- 
ferentiated. 
Peduncle or 
alimentary 
polyp and ge- 
nerative sac 
not differen- 
tiated from 
each other 
(see post). 
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 Stomohrachium we know nothing. 
Claparede has shown that gymnophthalmatous Medusas may 
produce Medusse 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 
