Mr. H. J. Carter on the Freshwater Infusoria of Bombay. 39 



ance of the ''nuclei/' These, however, might also secrete a 

 pellicula round themselves, and undergo the same kind of divi- 

 sion as the protoplasm, for they are endowed with a considerable 

 degree of contractile power, though not so active as that of the 

 protoplasm. Certain it is, that cells containing no nucleus, as 

 well as a cell containing one or more, will each produce a litter 

 of monads. 



These additional observations on the development of monads 

 from the cell-contents of the Characese will be better understood 

 after perusing the abstract of my paper entitled " Transforma- 

 tion of the Vegetable Protoplasm into AdinophrySy' to which I 

 have already alluded*. 



EXPLANATION OF PLATE L 



Fig, I . Spongilla alba, growing from the seed-like body : a, seed-like 

 body ; b, b, b, b, investing membrane charged with small spini- 

 ferous spicules ; c, c, parenchyma, consisting chiefly of globular, 

 ampullaceous sacs (8 to 10-5600ths of an inch in diameter), and 

 large, smooth spicules ; d, d, d, bundles of smooth spicules sup- 

 porting the investing membrane; e, e, openings of the afferent 

 canals ; /,/, dark points representing the apertures of the invest- 

 ing membrane ; g, tubular vent of the eflPerent system of canals. 

 N.B. — All the parts of this figure have been drawn upon the same 

 scale, in order that their relative proportions might be preserved 

 as much as possible. 



Fig. 2. Fundus of ampullaceous sac, representing the arrangement of the 

 sponge-cells in its substance ; the white or transparent lines indi- 

 cating the intercellular substance ; the central circle, which can- 

 not be seen in the same focus, pointing out the position of the 

 aperture on the opposite side. Sac 3^0 th of an inch in dia- 

 meter ; aperture or mouth TsV^th of an inch in diameter. This 

 figure is too elaborate : the sponge-cells should have been a little 

 fewer and larger. 



Fig. 3. Aperture or mouth of ampullaceous sac, showing the faint radiating 

 lines which appear when the sac is beginning to waste from want 

 of nourishment. 



Fig. 4. Sponge-cells of the ampullaceous sac, as seen after the Spongilla 

 has been torn to pieces : a, unciliated, b, monociliated forms 

 (active or secondary) ; a', 6', passive, spherical or primary, forms 

 of ditto. Unciliated cell from 2 to 3-5600ths of an inch ; mono- 

 ciliated cell from 1 to 2-5600ths of an inch in diameter. 



Fig. 5. Ideal section of an ampullaceous sac : a, diaphane, or cortical layer 

 (the existence of which is inferred, partly from the isolated sac, 

 fig. 9, presenting something of the kind) ; b, monociUated sponge- 

 cells with their cilia projecting into the interior ; c, aperture. In 

 this state this sac may sometimes be seen isolated, but with the 

 aperture closed, though the cilia are still undulating interiorly. 



Fig. 6. Portion of investing membrane illustrative of its apertures : a, aper- 

 ture fully dilated, showing the tubercle in its margin (nucleus of 



* Annals, vol. xix. p. 259, 1857. 



