22 
or rather less and about 1 mm. apart, have well developed lids which completely covers them. 
The main stem is devoid of cyclosystems along its lower half; they have been obliterated by 
rapid growth of the coenenchym; their previous situation is indicated by slight swellings. The 
ampullae occur on the lid. (Males only were found). Their growth swells the lid considerably, 
so as to make it dome-shaped; the surface is smooth (Fig. 23, I. 1). The roof or upper part 
of the dome breaks away when the spermatozoa are sufficiently ripe. In two cases where the 
lid has either been broken off at a very early stage, or else is abortive, the ampulla is formed 
at the region from which the lids usually spring. This species is most closely allied to the one 
next described. C. pachypoma. 
The species may be defined: 
Hydrophytum flabellate; surface smooth; cyclosystems oval, lids broad, generally rather 
larger than the cyclosystems they cover; ampullae on lid, surface smooth, distribution of male 
gonads by the breaking away of the upper half of the lid. 
3. Cryptohelia pachypoma sp. n. Plate II], figs. 24 and 25. 
Stat. 150? 0°6'N., 129°7’.2 E. Djilolo Passage. 1089 M. 4 pieces. 
This very pretty species forms an irregular flabellum, with non-anastomosing branches. 
The main stem and principal side branches are stout (3,7 mm. is the greatest diameter of the 
main stem), but the younger branches, which are numerous and closely placed, are very delicate, 
the stem at the base of a terminal branch being sometimes not more than 0,6 mm. The total 
height and breadth of the colony is about 40 mm. The colour is a pale yellowish white. The 
surface is scattered over with small perforated tubercles (Fig. 25 nem.); these occur especially on 
the posterior surface and on the sides, also often along the edge or surface of the lid and upon 
the ampullae: they are nematophores. Otherwise the surface appears to be smooth until it is 
calcined, when shallow, longitudinal grooves become apparent. The coenosteum between these is 
seen to be transversely striated. The cyclosystems are circular or nearly so, with a diameter of 
about 1,4 mm. and are generally about 0,6 mm. apart. They are obliterated on the thickest 
parts of the stem. In one or two cases there is a small group or a solitary cyclosystem on 
the anterior instead of the posterior surface of the flabellum. The ampullae occur upon the 
lids of the cyclosystem. Their formation is followed by great increase in size, so much so that 
adjacent lids sometimes coalesce. The specimens obtained were males. Three ampullae are 
usually formed on each lid, one towards the base and two further forward. This and the 
perforated tubercles already mentioned, give the ampullae a very nobbly appearance. In one 
or two cases where the lid has not been formed or has broken off at a very young stage, 
the ampullae have been formed at the base of where the lid would have been. The male 
gonads are not distributed by the breaking away of the upper half of the lid, as in C. ramosa, 
but as the stalk of attachment of the lid is not strong and the lid itself very bulky, the lid 
easily becomes detached as a whole and the spermatozoa escape. 
This species is most nearly allied to C. ramosa in the position of the ampullae but is 
distinguished from the latter by the smaller size of the colony, the round shape and smaller size 
