POLYGASTRICA. 63 



in the polygastric class of animals ; as many tribes have been 

 observed to be produced from ova or spawn, as well as by fis- 

 sure and gemmation. The Kolpoda cucullus {Jig. 20, 7) is 

 one in which Ehrenberg succeeded most perfectly in detecting this 

 kind of generation, but he has likewise observed it in many others. 

 The ova seem to be produced in the general parenchyma of the 

 body, without the visible existence of any organ specially destined 

 to their formation ; and, when mature, are expelled in a delicate 

 reticulate mass (Jig. 20, 8). Ehrenberg even describes some 

 contractile vesicles discovered to exist in many species, which he 

 regards, though perhaps without sufficient grounds, as being a 

 male apparatus provided for the fertilization of the ova previous to 

 their expulsion. In Paramecium aurelia (Jig. 17, 2) these were 

 two in number, (a, g,) placed at the two extremities of the body, 

 each seeming to consist of a delicate irritable central portion, 

 from which he could see, on gently pressing the animalcule be- 

 tween two plates of glass, eight canals issuing in a radiating manner 

 and diverging toward all parts of the body ; these became gradually 

 enlarged as the vesicle contracted, and, on the contrary, became 

 narrow and disappeared as the vesicle dilated. The contractile 

 organs were detected in twenty-two species belonging to very 

 different families ; but the radiating canals were only seen in two, 

 viz. Paramecium aurelia and Ophryoglena : their appearance in 

 Nassula elegans, Stentor polymorphus, and Euplotes charon, is 

 seen in Jig. 17 ; 1, 3, 4, b. The function of these organs 

 Ehrenberg believes to be connected with the secretion of a fecun- 

 dating fluid, which, being dispersed by their contraction through 

 the body, serves to fertilize the ova. 



(91 .) No circulation, properly so called, has been seen in 

 the polygastrica ; neither have vessels of any kind been satisfac- 

 torily made out. There is however in Paramecium aurelia, as has 

 been already mentioned, a constant sap-like movement in the gra- 

 nular matter of the body, which is easily detected, and was described 

 by Gruithuysen : this appearance Ehrenberg attributes to the 

 movements of the intestine ; but as we have been quite unable to 

 detect the arrangement which he indicates, or to reconcile the ap- 

 parent course of the globules with the supposed direction of the 

 alimentary tube, we are still inclined to regard the flow of particles 

 alluded to as analogous to what has been described as existing in 

 the stems of polyps. Neither do we find any distinct apparatus 

 devoted to respiration in these minute beings : the cilia upon the 



