438 Dr. Griffith on the Sacculi of the Pohjgastrica. 



LXI. — On the Sacculi of the Folijyustnca. By John William 

 GmrFiTii, M.D., F.L.S. &c. 

 To the Editors of tJie Annals of Natural Histoiy. 

 Gentlemen, 

 If you will find a place in yonr valuable Journal for these obser- 

 vations on the Poly gastric Animalcules, I shall feel obliged by 

 your inserting them. 



Your obedient servant, 

 John William Griffith, M.D. 



9 St. John's Square, May 8th, 1813. 



The real natm-e of the sacculi, vesicles, or stomachs which are 

 seen in the bodies of the Polygastric di\ision of Infusorial Ani- 

 malcules is a point which has occupied considerable attention, and 

 is at the present time by no means satisfactorily determined. The 

 extreme minuteness of these bodies renders their examination a 

 matter of very considerable difficulty, and what has hitherto been 

 discovered concerning their digestive cavities has been principally, 

 if not entirely, recognized by the introduction of foreign colom-- 

 ing matters into the sacs ; which colom-ing and other matters being 

 moulded by the compressing force or elasticity of the containing 

 sac or substance forming the walls of the cell in which they are 

 contained, assume its shape, and are readily distinguished from 

 the transparent parts of the animalcules Ijy their opacity or altered 

 refractive properties of light. Great difficulty is also experienced 

 in conducting the manipulations which are required for examining 

 such minute atoms, and an unusual share of patience and care. 

 The rajjidit}^ of their movements is also, without extreme caution, 

 liable to mislead the microscopic observer. 



It is well knomi that when the animalcules denominated Poly- 

 gastrica are examined imder the microscope, certain sac-like bodies 

 are observed in different parts of their bodies ; these are some- 

 times filled with various coloured particles, similar to those float- 

 ing in the water in which they live, sometimes merely mth fluid 

 or semifluid matters. These bodies, called by Prof. Ehrenberg 

 stomachs, are variable in number and situation, and in some cases 

 entirely absent. 



An opinion that these sacculi were ova was formerly entertained 

 by Gleichen, but this has long since fallen into disrepute ; and 

 justly so, inasmuch as the difi'erent matters which constitute the 

 food of these minute animals has been, and can readily be, traced 

 into the vesicles, which is sufficient to indicate then connexion 

 wdth the digestive and not the reproductive system. The Vorti- 

 cella, among many others, are particularly well adapted for the 

 examination of these sacculi, on accomit of their large size, fixed 

 position, or nearly so, and their great abundance. 



Si 



