64 ANATOMY AND PHYSIOLOGY 



of commerce consists of 20 atoms of fibroin, 1 atom of 

 iodine, and 5 atoms of phosphorus ; and in treating of the 

 physiological relations of fibroin as regards sponges, he 

 observes, " Its chemical constitution affords one of the 

 arguments why the Spongia should be classed among; 

 animals and not among plants, since in the vegetable king- 

 dom we nowhere meet with a substance in the slightest 

 degree resembling fibroin." 



From the general physiological characters of the skeletons 

 of the Sertularian and other Zoophytes, I had long suspected 

 that their component parts were identical, or very nearly 

 so, with those of the skeletons of the Spongiadse, and 

 I therefore applied to my friend, Mr. George Bowdler 

 B nekton, to assist me in determining this point, and he 

 very kindly undertook to make comparative qualitative 

 analyses with two species of Zoophytes, Sertularia oper- 

 culata and Flustra foliacea, with the fibres of Spongia 

 officinalis and of raw silk, and I cannot do better than 

 to quote entire the report of the results of his exami- 

 nation : 



" I have examined the Zoophytes you sent me, and 

 have compared their deportment under chemical agency, 

 with that shown by white silk and the fibre of ordinary 

 sponge. 



" All the specimens were treated in a similar manner, 

 being purified from foreign matter, as far as possible, by 

 boiling for two hours in water, and subsequently for the 

 same period in strong acetic acid. With the exception of 

 Flustra, the substances exhibited by this treatment little 

 change in their outward appearance. Carbonate of lime 

 enters so largely into the composition of Flustra, that its 

 disintegration by acids ought to cause no surprise. 



"From the results of the first seven experiments,* I 

 conclude that all these bodies contain the same, or a very 

 similar animal principle, which I suppose to be identical 

 with Mulder's fibroin. The varying colours of the pre- 

 cipitates from tannic acid and ammonia, I think is probably 



* Fora table of the results of the analysis of Mr. Bucktou, sec 'Philo- 

 sophical Transactions ' for 1863, page 740. 



