EXCRETOEY TUBULES IN AMPHIOXUS LANOEOLATUS. 489 



Excretory Tubules in Amphioxus 

 lanceolatus. 



By 



F. Ernest 'VTeiss, B.Sc, F.Ii.S., 

 University College, London. 



With Plates XXXIV and XXXV. 



In the spring of last year, through the kind permission of the 

 British Association for the Advancement of Science, I had the 

 privilege of occupying the table which the Association supports 

 at the Zoological Station in Naples. By the admirable arrange- 

 ments made at this station I was able to have a constant and 

 unlimited supply of living specimens of Amphioxus lanceo- 

 latus, and thought this a good opportunity to undertake 

 some experiments with a view to ascertaining whether the 

 curious patches of modified epithelial cells on the ventral wall 

 of the atrium of Amphioxus had any excretory function, as 

 Johannes Miiller (1) had held probable; and whether also 

 the atrio-coelomic funnels first described by Professor Ray 

 Lankester (2) in 1874^ and again more recently (3), had any 

 such function. 



Feeding experiments were made with Indian ink, carmine, 

 and Bismarck brown, the carmine alone leading to good results, 

 as the Indian ink is not able to be distinguished in the pig- 

 mented cells of the atrial cavity ; and the Bismarck brown, 

 though colouring the excreting cells very readily and deeply, 

 penetrated also into many other cells. 



Carmine is only very slightly soluble in sea water, but when 

 well ground up in a mortar it remains suspended in granules 

 suflSciently small to be taken up by the intestinal cells of the 



