HARDWICKE'S SCIENCE-GOSSIP. 



then again for some time it would send forth a 

 powerful stream, bearing the loose and floating 

 particles with it. During these alternate acts of rest 

 and activity, the oscula did not entirely close up, but 

 about June I, the large oscula gradually closed, 

 and the excurrent ceased to flow. The sponge then 

 became very pellucid, the ovaries of which were now 

 seen in every part of it, and the spicula standing out 

 in all directions. It had during the five months 

 increased in size to a little more than an inch in 

 diameter. From this time the sponge began to 

 diminish in size, and became very offensive. I then 

 removed it from the vase, and placed it in a small 

 glass globe, so that I could preserve the ovaries as 

 they became liberated. On August 18, I placed 

 several of the detached ovaries in a glass cell with 

 the view of witnessing the development and growth 

 of new sponge therefrom — the development com- 

 menced in ten days ; on August 28, I observed 

 that the foramens of several of them were open and 

 the gemmule or sarcode had issued out and was 



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Fig. 1. — Ovarium of Fresh-water Sponge : 

 it, the foramen ; b, first growth of sponge; 

 c, further extension of sponge. 



spreading on the bottom of the cell to which it was 

 firmly fixed. In fig. 1, is shown an ovarium with 

 the open foramen (at ft) out of which the sarcode 

 had escaped and was spreading on the glass around 

 the ovarium (l>). At this stage there was no spicula 

 visible, but a further extension of the sarcode or 

 growing sponge was seen (c). 



This new sponge is a very thin, gelatinous, semi- 

 transparent matter, which spreads on the bottom of the 

 glass, in which at first no spicula are seen, nor are 

 the pores rendered distinct, but in about seven days 

 the sponge had increased (as at fig. 2), and the grow- 

 ing spicula become numerous and extended over the 

 edge of the first formed part of the sponge (fig. 2,'e). 

 The sarcode is, as it were, festooned from point to 

 point of the spicula, as though the growing spicula 

 carried out with them the extending sarcode (fig. 2,f), 

 also the oscula, or excurrent canal is now formed 

 (fig. 2, g,) and the incurrent pores at h. I have seen 

 small portions of the sarcode separated from the 



growing new sponge, and in an amoeboid fashion 

 and form move slowly away from it, and settling 

 down at a distance from the ovarium, out of which 

 no doubt they originally came, and have seen them 

 growing as independent sponges, though very small 

 with their oscula extended, from which the excurrent 

 was seen to flow, as from the larger sponges. It is 

 stated by Bowerbank, " that one of the few modes of 

 the propagation of the spongiadse is by spontaneous 

 division of the sarcode." The current of water seen 

 to enter the pores (at //), and the excurrent out 

 through the oscula \g) is caused by vibratile cilia 

 with which the sponge cells are lined. These cilia I 

 believe have never been seen in operation in situ. 

 They are impossible to be thus seen, as they require 

 high power of the microscope to detect them, and that 

 cannot be applied to the pores of the living sponge, 

 as the mass of the sponge is too thick. With a view of 

 detecting, if possible, the cilia in a living sponge, 



■-■•— e 



Fig. 2. — Ovarium ; e, growth of spicula 

 ./, sarcode festooned on spicula ; g, oscula, 

 or excurrent canal ; //, incurrent pores. 



Mr. G. Gulliver, jun., B.A. Oxon, brought his 

 microscope, with a high power objective, and took 

 out one of the small growing sponges from the cell in 

 which I kept them, but the cilia could not be seen 

 until he tore the sponge to pieces with needles, there- 

 by breaking open the sponge cells, when the cilia 

 were plainly shown, lashing whiplike, and becoming 

 slower in motion as the death of the sponge ap- 

 proached, when the cilia became both rigid and 

 motionless (fig. 3,7). These openings, termed pores, 

 are lined with sponge particles, each of which is 

 provided with a vibratile cilium ; and as these cilia 

 work in one direction towards the excurrent canal, 

 they sweep the water out in that direction, and its 

 place is taken up by fresh water, which flows in 

 through the small apertures. The currents of water 

 carry along such matter as are appropriated by the 

 sponge particles lining the passages. I have observed 

 in close proximity to the new growing sponge, some 



