J. a. WALLER ON FRESH-WATER SPONGES. 47 



enabled to do. Previous to the observation thus recorded, I had 

 one with a gemmule (?) already perfected, which I discovered em- 

 bedded within the network of a piece of old sponge. It had evi- 

 dently passed through the stages I have mentioned, and had now 

 found a resting place for further development. I placed it in a 

 zoophyte trough, supplying it constantly with fresh water, and ob- 

 served it to be enveloped in a transparent membrane, defended or 

 strengthened by a few spicula. It was sub-globular in shape, and 

 of a bright emerald green colour (Fig. 3). I watched it daily. 

 New membrane was forming about it on the network of the old 

 sponge, and upon this new spicula (Fig. 4). This latter process was 

 interesting. First one was projected, another extended from its 

 apex, then one transversely. Additions were then made to the 

 first parallel to it (See Fig. 5), and so forth. 



Meanwhile the gemmule (?) was gradually increasing in size, 

 swelling out and becoming more ovate, and its granular character 

 more distinctly visible through the expanding membrane ; and 

 having been nearly a fortnight under observation, began now to 

 break up. The envelope burst, and its contents, consisting of 

 minute masses of sarcode, which, when aggregated together, had an 

 am^biform appearance, issued slowly from it (Fig. 6). Some of 

 them settled upon portions of the membrane of the sponge, or 

 upon the spicular network, and began to develope upon it. But 

 by far the greater quantity became effete, as, perhaps, the condi- 

 tions of life were little favourable for any further progress. 



During my observations I saw upon several occasions minute 

 bodies, ovate in shape, and having filiform appendages, moving 

 about on the edges of the protruding granular masses, with a singular 

 twitching motion ; but I could not bring a power of more than 60 

 diameters to bear upon them, and hesitate to express my belief in 

 their being spermatazoids, which are asserted to have been seen by 

 more than one observer, but which fact nevertheless remains in 

 obscurity. 



I have spoken of the phenomena described as of *' gemmation " 

 and the product as a gemmule, yielding in this to appearances 

 rather than believing the terms to be correct. A gemmule has 

 been described as " a vital mass separated from the parent, and 

 capable of being ultimately developed into a single individual, pos- 

 sessing the same specific characters and capabilities as the present 

 mass." But this clearly must be understood of those acts which 



