1892.] 



Note on Excretion in Sponges. 



483 



is insisted on by Lendenfeld ; the derivation of sponge fibres, onto- 

 genetically, by invagination of the outer surface, has been observed 

 by Barrois and 0. Schmidt; the probability that spongin arose as a 

 nitrogenous excretion has been suggested by Eisig. 



While I cannot ask space here to acknowledge my nnmerous ob- 

 ligations both at Cambridge and Naples, ifc is impossible not to 

 express my thanks to Professor Dohrn for his great kindness in 

 placing a table at my disposal in the Zoological Station.] 



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