1892.] 



Note on Excretion in Sponges. 



475 



Spicule, 



Fig. 1. — Living Metschnikoff cell, focussed through, the ectoderm. Some of its 

 granules are of yellow pigment, and some of the indigo which has been ad- 

 ministered. 



living, to many gentlemen working in the Zoological Station. I have 

 also successfully repeated the experiment several times, and (by the 

 use of concentrated corrosive sublimate with picrocarmine in sea- 

 water, followed by anhydrous alcohol and chloroform) have suc- 

 ceeded in making permanent preparations and sections showing the 

 blue indigo granules, the nuclei stained red, and, though somewhat 

 changed, the original pigment granules. 



In a Homoccel sponge found at Naples, corresponding with the 

 ordinary diagnosis of Ascetta primordialis, I found, after twenty- 

 eight hours in indigo- carmine, that while neither the . endoderm nor 

 the " mesodermal " tissue showed any tinge of blue, the flask-shaped 

 ectoderm cells were coloured faintly so, and the granules contained 

 in them strongly blue. The nuclei were colourless, thus excluding 

 the hypothesis of post-mortem staining, under which they colour 

 darkly. 



I have not yet observed with certainty the excretion of indigo- 

 carmine by the ectoderm cells of Ascetta clathrus ; the conditions 

 under which excretion is performed respectively by Metschnikoff 

 cells or ectoderm cells remain, therefore, still to be defined. But in 

 this sponge the appearance of the yellow granules in the two kinds 

 of cells is precisely the same, except that those in the Metschnikoff 

 cells are larger, being about 11 fx in average diameter, as opposed to 

 And of many characteristic reactions, such as extreme solu- 

 bility in distilled water, alkaline solutions, alcohol, and other fluids ; 

 solubility in dilute acetic acid, and insolubility in sea- water ; a 

 " port wine " colour, disappearing on heating, with iodine in sea-water, 

 and a nearly black colour with osmic acid, I have found no one 

 which differentiated the granules in the two kinds of cell.* 



All the forms shown by the Metschnikoff cells appear to be strongly 



* With reference to Topsent's observations ( ! Clionidae,' 1888, p. 48) on Cliona, 

 it is worth mentioning that in no part of A. clathrus is there any trace of a blue 

 reaction with sulphuric acid. 



VOL. LI. 2 K 



