290 On Merlia normani, Kirkp. 



The problem of the position of the Monticuliporas has 

 baffled several generations of geologists and zoologists, who 

 have regarded them as Foraminifera, Sponges, Ocelenferata, 

 or Folvzoa. At last a living organism has been found with 

 a skeletal structure showing many resemblances to these 

 Palaeozoic fossils. 



Sir John Murray informs me that he has seen a dry spe- 

 cimen of a coral-like organism from the West Indies in some 

 respects like Merita, and Prof. Stanley Gardiner has obtained 

 from the Indian Ocean somewhat similar specimens also dried. 

 These organisms have been spoken of as Foraminifera or 

 Alcyonarian Corals. Unfortunately, dried specimens afford 

 scaicely move information than that which is available for the 

 palaeontologist. I can only say that if the specimens referred 

 to are related to Merlia they are sponges. 1 have seen in the 

 British Museum a Foraminiferan from the Indian Ocean with 

 a surface reticulum and nodal tubercles, but the skeleton is 

 obviously Foraminiferan. 



I originally described Merlia as a Pharetron sponge 

 (' Annals,' Dec. Iii08, p. 510). Later {' Annals,' July 1909, 

 p. 47), I concluded that the upper part was a distinct siliceous 

 sponge, and at one time the organism seemed to me to be an 

 example of symbiosis between a siliceous and a degenerate 

 Pharetron sponge. Huxley, in his esssy on Hume, remarks 

 that if anyone stated that he had seen a Centaur careering 

 about in Piccadilly, we would feel justified, even if we believed 

 in the good faith and acumen of the narrator, in demanding 

 very strong proofs. If the statement were accepted, we 

 would perhaps wonder whether the Centaur were a Horse- 

 Man, a Man-Horse, or possibly, from some lurking doubt as 

 to the observing powers of the narrator, only a Man on a 

 Horse. 



It is at present believed that the Sponge Phylum originally 

 divided into three main branches (Calcarea, Triaxonia, Tetra- 

 xonia),and that the division between Calcareous and Siliceous 

 Sponges extends deep down to the very roots. The existence 

 of a sponge with a calcaieous and a siliceous skeleton had 

 seemed to me almost as improbable as that of a Centaur. So 

 it was not surprising that Merlia was regarded by me to be an 

 instance of symbiosis on a parallel with the Man-on-the-Horse 

 theory of the Centaur, and that I was misled into establishing 

 the genus Noronha, which must now become a nomtn nudum. 



The theory that Merlia is a siliceous sponge that has 

 " taken on " the function of forming a calcareous skeleton 

 appears at first sight to commend itself, because we seem able 

 to locate the sponge in a particular group of Monaxonellida, 



