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



the cell in which the aperture is situated?); b, aperture half- 

 closed ; c, wholly closed ; d, characteristic sponge-cell of invest- 

 ing membrane ; e, portion of a spiniferous spicule. 



Fig. 1 . Group of sponge-cells of the investing membrane illustrating their 

 arrangement in situ. 



Fig. 8. Figures illustrative of the development of the spicule : a, nucleated 

 sponge-cell bearing a spicule ^^o^h of an inch in length, and of 

 extreme thinness ; «', sponge-cell bearing a still younger spicule, 

 T^Wth of an inch in length, on which is seen the inflation; 

 b, ditto, with the spicule more advanced; c, spicule still more 

 advanced, showing the passage of the shaft through the inflation, 

 thus proving that the latter is the outer layer of the spicule, and 

 that the spicule is formed of layers deposited from within out- 

 wards; d, fully -developed smooth spicule; e,f.g, varieties in the 

 position and number of the inflations, and in the development of 

 the shaft, which are endless ; h, central portion of a spiniferous 

 spicule, showing two spines projecting from the inflation. 



Fig. 9. Isolated ampullaccous sac (TUoth of an inch in diameter), which, 

 havina: left the parent mass of Spongilla, has become amcebous 

 and actinophorous, presenting a cortical transparent portion (the 

 diaphane) externally, and the sarcode charged with granules in- 

 ternally. 



Fig. 10. Monociliated sponge-cell, after the constituent cells of the mass 

 of Spongilla have separated to seek an independent existence for 

 themselves : a, a, dotted lines showing the movement of the 

 surrounding particles of carmine in the direction of the arrows ; 

 b, a particle caught up and enclosed by a jirojection of the cell, 

 as in Actinophrys Sol; c, "granule;" d, contracting vesicles; 

 e, pedicle of attachment, which can be withdrawn at will. Cell 

 from 2 to 4-5600ths of an inch in diameter. 



Fig. 11. Section of a spherical group of the Uvella-iorm of sponge-cells 

 seen under similar circumstances (group rroth of an inch in dia- 

 meter): a, isolated group of three polymorphic cells; b, fixed iso- 

 lated on eproducing the same kind of currents with its cilium, &c., 

 as fig. 10 (a-fViri'd of an inch in diameter). 



Fig. 12. Amceba verrucosa, Ehr., al^^th of an inch in diameter: a,vesicula; 

 i), nucleus. This Rhizo])od generally contains a large portion of 

 Oscillatoria or a rotiferous animalcule for food, which has been 

 left out here for clearness. One of its characteristic features is 

 the elliptical form of the capsule of the nucleus or " nuclear 

 utricle," while the nucleus (" nucleolus") is spherical, and fre- 

 quently presents vacuoles. 



Fig. 13. The same, transformed into an ovisac partly filled with spherical 

 ovules in the granuliferous stage of development. Ovisac or 

 effete animal T^^^th of an inch in length ; ovule y^V e th of an 

 inch in diameter : a, early or nucleated form of the ovule ; b, in 

 granuliferous stage of development. 



Fig. 14. Euglena viridis, filled with ovules; compressed vertically ; pre- 

 senting the granular, ca])suled nucleus, and the vesicula with its 

 sinus. 



Fig. 15. Three figures to show how the fluid is expelled from the vesicula : 

 a, undistended state of sinus after it has just filled b, the vesi- 

 cula; o', sinus again becoming distended, and in-essing out the 

 contents of b', the vesicula ; a' , fully-distended state of the sinus 

 which has thus nearly emptied h", the vesicula, preparatory to 

 again discharging its contents into the latter. 



