324 GENERAL HISTOHY OF THE INFUSORIA. 



" The processes above described are those usually observed when a suitable 

 specimen is placed so that it cannot move, or only move very little, upon the 

 slider. If, however, a Bursaria is compressed somewhat more with the co- 

 vering-glass, or if the water on the slider is almost all evaporated, some other 

 peculiar phenomena present themselves, not only in the contractile vesicle, 

 but in the vessels. The last diastole coming perfectly to rest, and nothing 

 unusual being observed, except that the reservoir is more elongated, with the 

 systole appear suddenly two contractile vesicles instead of one ; that is, a 

 portion of the surrounding substance makes its way across the middle of the 

 contractile vesicle while it is contracting, and thus divides it into two parts. 

 Each of these two new reservoirs has its own systole and diastole. In- most 

 cases their contractions do not occur at the same moment. Each is in con- 

 nexion with those vessels which opened into it before the separation. The 

 vessels exhibit the same play as if there were but one uninjured contractile 

 vesicle. Sometimes the two reservoirs reunite into a single one. I saw this 

 happen duiing a diastole which occurred exactly simultaneously in both : they 

 advanced near together, projected out points toward each each other, which 

 came in contact and formed a dumb -bell- shaped reservoir ; and this was ra- 

 pidly converted into a globular vesicle, which contracted and expanded as at 

 the origin. 



" Yon Siebold has already observed in Phialina vermicularis, Bursaria 

 cordiformis, &c., ' that in strong contractions of the whole body, a largish 

 round pulsating space was di-awn out longitudinally, constricted in the mid- 

 dle, 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 reservoii^s. These enlargements are not, 

 however, subject to rhythmical disappearance and reappearance, but are per- 

 manent ; they are filled with the same colourless fluid as the contractile vesi- 

 cles, 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 connexion 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 sub- 

 stance, while part do not. 



" I have not succeeded in any ease in isolating a membrane of the contrac- 

 tile reservoir or of the vessels. I find no trace of cilia in the interior of the 

 vascular system. This alone suflices to distinguish essentially those Infusoria 

 furnished with vessels from the Distoma-Qmbijo in which G. E. Wagener has 

 discovered ciliated vessels. 



'' Diff'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 contradtHe vesicles as 

 organs of the cu^culation. As to the direction in which the fluid flows in the 

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

 ceive 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 

 externally ? 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, in the most minute examination, he was 



