25 
they, too, are devoid of tentacles and (probably) possess a 
mouth-opening, the terminal end sometimes appearing trumpet- 
shaped. 3) The medusæ. The largest buds are elongated, cylin- 
drical; in the fixed state they do not develop more than two, 
clumsy tentacles; their surface is speckled with nematocysts (most 
distinctly seen in the younger stages, still before the medusoid 
shape is recognizable). When liberated — the fish was kept in an 
aguarium, and great numbers of medusæ were set free — they at 
first resemble a young Stomatoca (the medusa of Perigonimus), 
having an ovoid, upwards rounded bell, four simple radial canals 
and ring-vessel, and a proboscis with entire mouth. Later the 
medusa acquired four tentacles, two new growing out in the inter- 
space of the two first formed. When all four are fully developed 
it resembles a Sarsia. In this stage, possessed of four long and 
slender tentacles, the medusæ sank to the bottom and died. 
If we suppose that the medusæ of Ichthyocodium, when set 
free, also acquire four tentacles — which seems to me at least 
probable — they would agree with those of Hydrichthys; in the 
attached state, as buds, the likeness is practically complete. The 
differences of some amount between Hydrichthys and Ichthyocodium 
are the following: 1) the basal membrane in the first is firm, leathery; 
2) the polypes are of two kinds, sterile and fertile ones; 3) the 
medusæ-buds are clustered on the ends of branches or stalks from 
the fertile polypes. According to the figures given by Fewkes 
(the author does not give any measurements of the polypes, buds or 
medusæ), the size of the colony in Hydrichthys surpasses that of 
the largest Jchthyocodium found; but it is by no means impossible 
that the latter may acquire a larger size and fuller development 
than the specimen figured Pl. I, fig. 1. 
"In 1907 R. E. Lloyd described a ANudiclava monocanthi 
growing on the fish Monocanthus tomentosus trom the Andamana- 
Sea (13). Like the preceding this Hydroid is attached by means 
of a naked basal membrane, containing tubes from which naked, 
claviform hydranths without tentacles grow (0,75 mm. in length) ; 
