Mr. H.J. Carter un the Organization of Infusoria. 131 



Of the use of the vesicnla, and its vascular system, we are at 

 present ignorant, further than tliat its functions are excretory ; 

 and when we observe the quantity of water that is taken into the 

 sarcode with the food, and try to account for its disappearance, 

 it does not seem improbable that the vesicula and its vessels 

 should be chiefly concerned in this oftice. Another semce, 

 however, which it performs, is to burst the spherical membranes 

 of Vorticella and Plcesconia when they want to return to active 

 life after having become encysted : this it effects by repeated 

 distension, until the lacerated cyst gives way sufHciently lor the 

 animalcule to slip out. At these times, also, the animalcule is 

 rendered so sj)herical by this distension that it is also evidently 

 one way by which the Infusoria might assume this form (fig. 12). 

 Hence, in describing the sarcode, I have expressed a doubt 

 whether ihc water in an AmoRba, when distended in this manner, 

 be in its centre or in the cavity of the vesicula. Certainly, when 

 Amoeba is in the form of a sphere, I never have been able to see 

 the vesicula, while all the other elements of the cell have been 

 perfectly plain ; added to which, under these circumstances, a 

 part of the cell-wall is generally transparent, from the absence 

 of the sarcode and its granules, which would be the case if the 

 vesicula were the cause of the distension, since in Amceba it is 

 attached to the pellicula, and therefore no sarcode exists imme- 

 diately opposite this point (fig. 13). 



Should it have any other uses, they are probably similar to 

 those of the " Water Vascular System " of Rotifera, which in 

 Brachionus Pain, one of the largest species of this class, consists 

 of a corrugated sac when empty (like the bladder of mammalia), 

 opening by a constricted neck into a heart-shaped cloaca close 

 to the termination of the alimentary canal ; and, when distended, 

 presenting {mild) a single vessel opening into its fundus, and 

 then passing down through its side towards the neck, where it 

 divides into two, which respectively run up laterally to the an- 

 terior extremity of the body, bearing in their course four mono- 

 ciliated (Huxley)* pyriform diverticula, and probably termi- 

 nating, as in Lacinulariaf, partly in junction and partly in blind 

 tubes. The vacuolar structure attached to these vessels may be 

 analogous to the vacuolar structure connected with the vesicula 

 in the Infusoria, and it would be interesting to determine if the 

 vacuoles in it occasionally diminish in size or disajjpear, or be- 

 come dilated when from disease or approaching death the vesi- 

 cula itself is unnaturally and permanently distended. Should 

 the lateral vessels not terminate in Brachionus Pala, as above 

 mentioned, then they nmst, as appears to be the case in the other 



* Quart. Jouru. Microscoj). Sc. vol. i. p. 7- t Idon. 



9* 



