212 Dr Gairdner's Analysis of 



animal kingdom, the utmost variety in respect to form, situation, 

 and degree of complication. It is in the Monas termo, pulvis- 

 cultis, and other larger monads, simply a round sac in the centre, 

 and occupying the greater part of their bodies. In the genera 

 Enchelys, Paramcecium, and Kolpoda, it assumes the form of a 

 long intestinal canal, traversing the greater part of the body, 

 and at times convoluted in a spiral manner, which is furnished 

 with a great number of caecal appendages, or stomachs ; this 

 sinorular disposition, of which no other example occurs in the 

 animal kingdom, is particularly distinct in the Leucophrys pa- 

 tula. That these blind sacs are real stomachs, and do not at all 

 correspond to the caeca of other animals, is evident from the fact 

 of their being filled with colouring matter immediately on its 

 being received at the mouth, or anterior orifice of the canal. 

 The tubes which connect these sacs to the main canal of the 

 intestine, vary very much, both in length and in diameter, as 

 well among the different caeca, as in the same one at different 

 times, being usually in a state of great contraction, and at 

 times scarcely perceptible when the cavity to which it belongs 

 is empty, and may be supposed not to be in a state of activity*. 

 We can count from 100 to 200 of these sacs in the course of the 

 intestine of the Paramcecium Chrysalis and Aurelia. When 

 they are filled with colouring matter, the common intestinal tube 

 is usually quite empty and transparent ; this, joined to the bluish, 

 reddish, or greenish tint which they often assume when empty, 

 may have been the reason that these sacs were mistaken by 

 Miiller tor ova, and by Schweigger for internal monads still ad- 

 hering to the parent trunk. In other infusoria, as the Rotifer 

 vulgaris, the alimentary canal is in the form of a slender tube, 

 and extending nearly the whole length of the body, and termi- 

 natino- at its anal extremity in a dilatation or cloaca for the re- 

 ception of the ova and the male seminal fluid, previous to its 

 termination at the surface of the animal. Others of larger di- 



• Attention must be paid to this circumstance, as, from the colourless 

 transparency of the intestine when empty, and in a state of contraction, very 

 erroneous ideas may be formed of the number and connexions of the sto- 

 machs of some of these auinvils, when they are separately filled with colour- 

 ing matter. The alimentary canal, too, may be filled with water, and may 

 lien verv much resemble some forms of tlie ovaria. 



