1900] MICROSCOPICAL JOURNAL. 107 



cosmopolitan and showing also the opinions of naturalists 

 to the species also. Both Dr. Bowerbank and Mr. Carter 

 were inclined to make it a sponge from visual examina- 

 tion and not from physiological grounds. And here I 

 will strongly urge the physiological ground for the def- 

 finition of forms, for species are visual and forms are 

 physiological. The physiological ground can be worked 

 to an unlimitted extent if need be. The optical ground 

 can be turned to a microscopical use in the case of min- 

 ute organisms only, and therefore is unreliable. But I 

 have already said this in other publications. 



The optical appearance of the organism in question was 

 a sponge and the physiological agreed for itcould be only 

 from the soundings. But it is my wish to point out here 

 that on physiological grounds the organism was neither 

 a diatom (although placed there understandingly) nor a 

 sponge, but belonged to the order of Protista, organisms 

 that have neither the properties of a plant (diatomacean 

 or bacillarian),nor animal (sponge), but which live by means 

 of matter which is absorbed into the mass not by a mouth 

 but by a membrane of some substance which has the 

 properties of cellulose but is not. It neither absorbs car- 

 bonic anhydride as plants do, nor nitrogen as Bacteria do 

 (plants) ? or Fungi (plants also), Radiolaria (animals), or 

 Spongidae, (animals also). By means of this membrane, 

 it absorbs by diffusion, the silica from the hydrate of 

 silica in the water and deposits it inside the membrane, 

 and this it does as a Protistan and a plant (Bacillaria or 

 Bacteria or Fungi) or animal (Radiolarian). So that the 

 lower organisms are the same physiologically or optically 

 and cannot be distinguished in any way. 



Another fact : In all the soundings made by the" Val- 

 orou8"and "Challenger" in the Pacific and Atlantic oceans, 

 and also in the soundings brought home by theTuscaro- 

 ra, as well as in gatherings containing living forms every- 

 where, the most common Bacillarian is the Coscinodiscus 



