40 Prorre(h'nqs of the lioi/nl Irish Acmlcmij. 



was there any allowance made for different stages of development. As a 

 result of this, three species— viz., J. fragilis, J. flexilis, and J. harhadensis — 

 were established on what must now be regarded as young colonies of this 

 species. The large number of specimens, which undoubtedly belong to this 

 species which we have been able to examine in detail with respect to the 

 differences on which these three species were based, confirm beyond doubt 

 the opinion of several authors — notably Ridley, Studer,Hickson, and Thomson, 

 that these cannot be regarded as distinct. 



I give here a short description of these three species, followed by a 

 systematic study of a large number of specimens which may help to give a 

 true estimate of the variability of certain characters and the constancy of 

 others, and so form a basis for a definite specific diagnosis. 



J. fragilis Ridley. 



In 1884 Ridley established the species fraf/ilis for two specimens from 

 Queensland with the following characteristics : — Stem long, unbranched, 

 diminishing very slowly to the tip, which may be either clavate or sharp- 

 pointed, flexible, and easily broken. The diameter at the base is 5 mm., at 

 the apex 3-4 mm., except when the apex consists of a fine point. The cortex 

 is thick and creamy-white when dry ; there is no trace of a lateral line in 

 the upper three-fourths. The verrucae are small, about 1 mm. in height, 

 clavate, closely adpressed against the cortex, crowded over all parts ; axis 

 very slender, about 1 mm. in diameter at the base and hair-like at the apex ; 

 near the base it is olive-brown, hard, and beset with longitudinal striae. 

 The cortical spindles are the same as in J. gemmacca. He points out the 

 following differences between this species and J. gemmacea : — 



(1) The verrucae are small and crowded. 



(2) There are no lateral lines in the upper three-fourths. 



(3) The colour is pale creamy-white. 



(4) The heads of the double stellate spicules are more abundantly 



tuberculated. 



Later, in 1887, Ridley referred, with doubt, two colonies from Mergui to 

 this species as a variety. One of these was white or cream-coloured, the 

 other was pale brick-red. He notes that these specimens approach J. juncea, 

 which, he says, is distinguished from J. frdgilis by its greater size, its red 

 colour, its larger and more distant polyp-verrucae, the presence of a space 

 bare of verrucae above the base and by the possession of equal-ended double- 

 stars. These specimens, he says, stand midway between_;wiia'« a,ad fragilis. 



