268 N. Ann AND ALE : Notes on Freshwater Sponges. [VOL. I, 



spicules are produced towards the ends of the primary skeleton 

 fibres and spread out in one plane so as to have a fanlike outline ; 

 in such buds the form is more flattened and the distal end less 

 rounded than in others, and the superficial area is relatively 

 great, so that they float more readily. Those buds that sink, 

 usually fall in such a way that their proximal, flattened end 

 comes in contact with the bottom or some suspended object, to 

 which it adheres. Sometimes, however, owing to irregularity of 

 outline in the distal end, the proximal end is uppermost. In this 

 case it is the distal end that adheres. Whichever end is upper- 

 most, it is in the uppermost end, or as it may now be called, the 

 upper surface, that the osculum is formed. Water is drawn into 

 the young sponge through the pores and, finding no outlet, accu- 

 mulates under the dermal membrane, the subdermal space being at 

 this stage even larger than it is in the adult sponge. Immediately 

 after adhesion the young sponge flattens itself out. This process 

 compresses the water in the subdermal space and apparently 

 collects a large part of it at one point, which is usually situated 

 near the centre of the upper surface. A transparent conical 

 projection, formed of the dermal membrane, arises at this point, 

 and at the tip of the cone a white spot appears. What is the 

 exact cause of this spot I have not yet been able to ascertain, 

 but it marks the point at which the imprisoned water breaks 

 through the expanded membrane, thus forming the first osculum. 

 Before the aperture is formed, it is already possible to distinguish, 

 on the surface of the parenchyma, numerous channels radiating 

 from the point at which the osculum will be formed to the 

 periphery of the young sponge. These channels as a rule persist in 

 the adult organism and result from the fact that the inhalent 

 apertures are situated at the periphery, being absent from both 

 the proximal and the distal ends of the bud. In the case of fioat- 

 ing buds the course of development is the same, except that the 

 osculum, as in the case of development from the gemmule in other 

 species (see ZykoiT, Biol. Ceniralb., xii, p. 713, 1892), is usually 

 formed before adhesion takes place. 



The life of the individual is very short in 5. proliferens , never 

 lasting for more than a few weeks. So far as I have observed, 

 sexual reproduction does not take place, but gemmules are pro- 

 duced in large numbers at the same time as the buds, often when 

 the sponge is less than 100 sq. mm. in superficial area. A continuous 

 succession of generations takes place throughout the year. 



The above observations have been made chiefly on specimens 

 in my aquarium in the Museum, but they have been corroborated, 

 as far as possible, by a periodical inspection of others living in 

 natural conditions in a pond. 



Buds of a somewhat different nature are sometimes produced 

 by S. carteri Bwk., and appear to be identical with the repro- 

 ductive bodies described in S. lacustris by Laurent (C r., Se. Ac. 

 Sc. Paris, xi, p. 478, 1841) many years ago. With these I hope 

 t6 deal on another occasion. 



