I 



M. N. Lieberkuhn on the Anatomy of the Infusoria, 337 



together, projected out points toward each other, which came in 

 contact and formed a dumb-bell-shaped reservoir, and this was 

 rapidly converted into a globular vesicle, which contracted and 

 expanded as at the origin. 



Von Siebold has already observed in Phialina vermicularisy 

 Bursaria cordiformis, &c., " that in strong contractions of the 

 whole body, a largish round pulsating space was drawn out 

 longitudinally, constricted in the middle, and at length was 

 separated into two smaller round spaces, — exactly as occurs 

 when a drop of oil is separated into two portions/' During the 

 above-described alterations in the contractile vesicles, alterations 

 ordinarily take place in the vessels also. Thus expansions appear 

 in them at points lying very distant from the contractile reser- 

 voirs. These enlargements are not however subject to rhythmical 

 disappearance and reappearance, but are permanent ; they are 

 filled with the same colourless fluid as the contractile vesicles, 

 and are mostly globular or ellipsoidal. If such enlargements 

 of the vessels are seen in specimens which, from unfavourable 

 optical conditions, do not display the vessels themselves, they 

 may be taken for vacuoles (in Dujardin's sense). Their con- 

 nexion with the vessels, and their mode of origin, which is 

 readily accessible to observation, prove that they are totally 

 distinct from the vacuoles in the interior of the body, part of 

 which contain nutrient substance, while part do not. 



1 have not succeeded in any case in isolating a membrane of 

 the contractile reservoir or of the vessels. I find no trace of 

 cilia in the interior of the vascular system. This alone suffices 

 to distinguish essentially those Infusoria furnished with vessels, 

 from the Distoma-emhvyo in which G. R. Wagener has discovered 

 ciliated vessels. 



Difi^erent hypotheses have been put forth in explanation of the 

 function of the contractile vesicles. There is a detailed account 

 of these in Claparede's paper on Actinophrys^. Claparede 

 rightly explains the contractile vesicles as organs of the circula- 

 tion. As to the direction in which the fluid flows in the vessels, 

 nothing can be directly observed in most cases, since we cannot 

 perceive in the fluid any solid corpuscles at all similar to the 

 blood-corpuscles of other animals. Is it a perfect circulation ? 

 or does the fluid flow back again in the same vessel in which it 

 has been propelled forward by the contractile vesicle ? or are 

 the contents of the contractile vesicles constantly expelled ex- 

 ternally ? The last view has been set up by Oscar Schmidt. 

 He states that he has seen the place of exit in the genera 

 Bursaria and Paramecium, Claparede is opposed to this, since, 



* Ann. and Mag. Nat. Hist. ser. 2, xv. p. 211. 



