All the Amphidiscophora have Lyssacine skeletons; in the Hexasterophora both types of skeleton occur. The subdivision of the Hexasterophora is determined by the presence or absence of uncinate spicules. An "uncinatum" is a diactine spicule, pointed at both ends and bearing barbs all directed towards one end. This method of classification gives us a wholly Dictyonine order, UNCINATARIA, and an order consisting partly of Dictyonine, partly of Lyssacine genera, which may be distinguished as the ANUNCINATARIA. {204}Ova have rarely been found, and sexually produced larvae never; but Ijima has found archaeocyte clusters in abundance, and his evidence is in favour of the view that they give rise asexually to larvae, described by him in this class for the first time (see p. 231). Both sub-classes are represented in British waters: the Amphidiscophora by _Hyalonema thomsoni_ and _Pheronema carpenteri_; the Hexasterophora by _Euplectella suberea_ and _Asconema setubalense_, and of course possibly by others. _Hyalonema thomsoni_, one of the glass-rope sponges, was dredged by the _Porcupine_ off the Shetland Islands in water of about 550 fathoms. The spindle-shaped body of the sponge is shown in Fig. 97. Its long rooting tuft is continued right up its axis, to end in a conical projection, which is surrounded by four apertures leading into corresponding compartments of the paragaster. [Illustration: FIG. 97.—_Hyalonema thomsoni._ A, Whole specimen with rooting tuft and _Epizoanthus_ crust; B, pinulus, a spicule characteristic of but not peculiar to the Amphidiscophora, occurring in the dermal and gastral membranes; C, amphidisc with axial cross; D, distal end of rooting spicule with grapnel. (After F. E. Schulze.)] The crust of Anthozoa of the genus _Epizoanthus_ (p. 406) on the rooting tuft is a constant feature in this as in other species of _Hyalonema_. It contributed to make the sponge a puzzle, which long defied interpretation. The earliest diagnosis the genus received was the "Glass Plant." Then the root tuft was thought to be part of the _Epizoanthus_, which was termed a "most aberrant Alcyonarian with its base inserted in a sponge"; next we hear of the sponge as parasitic {205}on the Sea Anemone. Finally, the root tuft was shown to be proper to the sponge, which was, however, figured upside down, till some Japanese collectors described the natural position, or that in which they were accustomed to find it. _Pheronema carpenteri_ was found by the _Lightning_ off the north of Scotland in 530 fathoms. The goblet shaped, thick walled body and broad, ill-defined root tuft are shown in Fig. 98, but no figure can do justice to the lustre of its luxuriant prostalia and delicate dermal network with stellate knots at regular intervals. The basalia are two-pronged and anchor-like. [Illustration: FIG. 98.—_Pheronema carpenteri._ × ½. (From Wyville Thomson.)]