J. G. WALLER ON FRESH-WATER SPONGES. 45 



filled up the bottle with fresh water and set it aside out of the direct 

 light, where it remained all the winter. About the middle of March^ 

 1871, I examined it, and observed a green spot on a fragment of the 

 old sponge left in the autumn. On applying a lens to the side, I 

 was delighted to find it was a young sponge developing its mem- 

 branes upon it. Considering the decomposition to which I have 

 referred, I did not expect such a result. 



But instead of giving an account of this, which was some- 

 what advanced in development, I will select another example, which 

 I found as a minute white speck upon the side of the bottle, thereby 

 rendering it easy of examination. It consisted entirely of a pel- 

 lucid membrane, supported or strengthened by spicula which 

 projected slightly from its surface, enclosing denser granular 

 matter, in which the pores could easily be detected by an inch 

 objective. The osculum was remarkably developed, but being 

 situated on the other side of the sponge was not always visible ; 

 yet I had frequent opportunities of examining this curious organ. 

 It was a transparent tube, generally somewhat larger at its distal 

 extremity, often very long in proportion to the mass of sponge when 

 fully extended, corrugated in structure and frequently having upon 

 its surface a spiculum here and there without any order. One end 

 of the sponge was attached to an ovarian capsule, divested of its 

 outer integument and spicula. This served throughout my obser- 

 vations as a pointer, for, being a fixed object, it indicated the nature 

 of the changes, both of position and of form, which took place 

 from day to day. These are difficult to describe, but will be un- 

 derstood by aid of the accompanying figures, selected from the 

 numerous drawings made. 



Plate iii. Fig. 1 represents the sponge when first discovered, May 

 18. The following show the successive changes according to dates 

 annexed : — Fig. 2, May 25 ; Fig. 3, May 31 ; Fig. 4, June 7 ; Fig. 

 5, June 10 ; Fig. 6, June 12 ; Fig. 7, June 15 ; Fig. 8, June 

 17. The last shows the condition just before it separated. 



The nature of the development was a contraction, so that the 

 flat membranous expansion was drawn by degrees into another 

 shape, denser in character, and gradually taking a globular form. 

 During this process some of the external spicula of its network 

 were left upon the sides of the glass ; and on the 7th day after my 

 observations began a faint tinge of green was visible in the central 

 portion. This colour increased daily with the progress of con- 



