204 



PORIFERA 



Fig. 97. — ITyaloaema thnmscni. A. 

 Whole specimen with rooting tuft 

 and Epizoanthus crust ; B, pinulus, 

 a spicule characteristic of but not 

 peculiar to tlie Amphiiliscophora, 

 occurring in tlie dermal and gastral 

 membranes ; C, amphidisc with 

 axial cross ; D, distal end of root- 

 ing spicule with grapnel. (After 

 F. E. Schulze.) 



inserted in a sponge " ; next 



Ova liave rarely beeii found, and 

 sexually produced larvae never ; but 

 Ijiina has found archaeocyte clusters 

 in abundance, and his evidence is 

 in favour of tlie view that they 

 give rise asexually to larvae, described 

 by him in tliis class for the first 

 time (see p. 231). 



Tioth sub-classes are represented 

 in British waters : the Amphidisco- 

 pliora by Hyalonema tlwmsoni and 

 Pheronema carpenteri ; the Hexas- 

 terophora by Ewpledella suberea and 

 Asconema setvhalense, and of course 

 possibly by others. 



Hyalonema thomsoni, one of tlie 

 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 corre- 

 sponding compartments of the 

 paragaster. 



The crust of Anthozoa of the 

 genus Epizoanthus (p. 406) on the 

 rooting tuft is a constant feature in 

 this as in other species oi Hyalonema. 

 It contributed to make the sponge 

 a puzzle, which long defied inter- 

 pretation. The earliest diagnosis 

 the genus received was the " Glass 

 Plant." Then the root tuft was 

 thought to be part of the Epizo- 

 anthus, which was termed a "most 

 aberrant Alcyonarian with its base 

 we liear of the sponge as parasitic 



