37'2 il//-. Hogg's Observations on the Spongilla fluviatilis, 



I felt assured of the extreme likelihood, nay, almost certainty, of their being 

 identical. And with the view of ascertaining- whether they were or not such 

 animalcula, I put several of the germlike bodies into a wine-glass full of 

 spring-water, adding fresh daily to them ; after a day or two their gyratory 

 motions became weaker and slower, and at length they entirely ceased : then 

 the bodies attaching themselves to the bottom and sides of the glass, and 

 losing their original shape, became flatter ; the transparent membranes of 

 their upper portion disappearing, the white opake portions alone were left, 

 which, resembling minute specks, at the expiration of a few more days in- 

 creased to such a sufficient size as to show, with the aid of a magnifier, that 

 they are undoubtedly the rudiments of the Spongilla itself, and thus proving 

 that they are its reproductive bodies or sporules, and not merely, as I had con- 

 jectured, parasitical Infusoria*. I have taken the liberty of bringing for ex- 

 hibition this evening that same wine-glass, wherein the small specks are di- 

 stinctly seen, and which, when submitted to inspection under a microscope, 

 will be found to be the commencements of the Sponge, in which the young 

 fibres or spicula are already visible. 



One of these bodies I likewise put by itself in a watch-glass containing a 

 little water, which I placed on the stage of the microscope for the purpose of 

 continuing to witness with that instrument more minutely its process of 

 development ; the water being changed two or three times a day, the germ- 

 like body at first moved a good deal about the glass ; it then began to keep 

 nearly in the same place, only turning gently round as if on its axis ; be- 

 coming afterwards stationary, it fixed itself to the glass, and changed into 

 a small spot of a white opake substance ; which, while growing in the 

 water, appeared under the microscope to be solely gelatinous, but when it 

 had been dried for a day or two, minute cells and fibres or spicula were ma- 

 nifest. 



At this time I was repeating the experiment of growing the Spongilla from 

 its seedlike sporidia or sporules, as I had only imperfectly done so in the 

 preceding March. Having taken many of these fresh seedlike bodies from 



* I must say, tliat it is probable that some of those bodies which are now referred to the Infusoria 

 will hereafter turn out to be only the sporules of certain fluviatile and marine plants. 



