56 
GUIDE TO THE CORAL GALLERY. 
Case 3, detached from the flower -like stocks of Athecate Hydroids come 
Upright part. . un( j er the Antliomedusce ; they have naked eye-spots (Fig. 4), and 
the eggs are formed in the walls of the manubrium ; see Ratkkea 
fasciculata * a little Medusa which is given off from a small solitary 
fixed polyp with four tentacles. The early history of Pandcm 
conica* and Tiara pileata * both of which are Anthomedusw , is 
unknown. 
The Medusas of the Thecate Hydroids come under the Leptomedi/sce 
(see Obelia * Case 3, and Model of Rliegmatodes tlialassina ) ; the eggs 
are formed in the radial canals, and the sense- 
organs are either eye-spots or “ litho-cysts,” 
the latter being vesicles containing a hard 
concretion which transmits impressions from 
the outside to delicate “ auditory ” cells. In 
certain Hydromedusce the sense-organs arise 
on modified tentacles known as tentaculo-cysts. 
These forms, which come under Haeckel’s 
Orders Trachomedusai and Narcomedum, have 
no known “ Hydroid history,” and in some 
cases are known to develop direct from the 
egg ; see Carmarina hastata (Fig. 20), and 
Model in Case 3a. Two fresh-water Medusae 
are known, both of which are Hydromeduscr 
Limnocodium sowerbii , from the Victoria Regia 
Tank in the Royal Botanical Society’s Gardens, 
has a shallow umbrella less than half an inch 
in diameter and with numerous tentacles ; 
the fixed phase occurs as a columnar polyp 
about a quarter of an inch in height, simple 
or branched once or twice ; medusa buds 
Portion of Astylus show- arise from the summit ; the original habitat 
w«h cy a ' “central 8 was probably the Amazon region. The second 
tropore and zone of species, Limnocnida tanganyiccR , comes from 
(AfTe^loseley 1 ) 130168 Lake Tanganyika ; the umbrella is about 
an inch across, the manubrium is very 
wide and shallow, and the stomach-cavity is nearly filled up by 
the convex lens-like central area of the under surface of the 
umbrella. 
Case 3, Finally the Medusas of Millepora and the swimming-bells, &c., of 
Upright part. ^ Sipfl 0 nophora belong to the Hydromedusan type. 
Scyphomedusan Medusa ( Scyphomedusce ). These include the 
