34 Mr. II. J. Carter on the Freshwater Infusoria of Bombay. 



know the structure of the ampuUaceous sacs, seems very intelh- 

 gible ; for we have ouly to conceive an enlargement of the small 

 sponge-cells lining its interior, with the addition of ovules to 

 them respectively, and the spicule-bearing sponge-cells of the 

 cortical substance supplying the spicular crust to the exterior, 

 to have a globular capsule thus composed, with a hilum precisely 

 like the seed-like body; a conjecture which seems to derive 

 support from the fact, that in some instances, when Spongilla is 

 beginning to experience the want of nourishment, these sacs, 

 small as they are, assume a defined, rigid, spherical form, from 

 their pellicle becoming hardened and encrusted with extremely 

 minute spicules. 



Additional Notes on the Freshwater Infusoria in the Island of 

 Bombay. 



As there are some parts of my " Notes" on the organization 

 of the Infusoria* which require correction, alteration, and further 

 explanation respectively, I take this opportunity of commu- 

 nicating the observations necessary for this purpose, and at 

 the same time of supplying additional matter, which will render 

 them more complete. 



Vesicula. — At p. 129 it was stated that the existence of the 

 vesicula '^in Astasia, Anisonema (Duj.), and Euglena can only 

 be determined by inference." Since then I have seen the hya- 

 line vesicle, supposed to be the vesicula, empty itself in all three 

 of these organisms, but more particularly in Euglena viridis, 

 and a description of the process, which is peculiar, in this species 

 will serve for all the rest. (PI. I. fig. 14.) It has been already 

 stated, that in Anisonema the vesicula seemed to alter in size 

 and shape without completely contracting, which is more or less 

 the case with all this class of animalcules, and appears to arise 

 from the presence of a single sinus in connexion with the vesicula, 

 as will be seen by the following description of the mode in which 

 this function is performed. 



In Evglena viridis the single sinus, which is attached to the 

 side of the vesicula, after having become filled, pours its contents 

 into the latter; the vesicula, thus distended, is now pressed 

 upon by the gradual refilling of the sinus, and thus its contents 

 also become evacuated. Hence we never witness that sudden 

 contraction of the vesicula which is so common in other Infu- 

 soria, at the same time that it often appears double in Astasia 

 and Anisonema (where it is more evident than in Evglena, owing 

 to the absence of colouring matter), from both sinus and vesicula 

 being more or less distended together (fig. 15). 



* Annals, vol. xviii. p. 115, 1856. 



