322 GENERAL HISTOET OF THE INFUSORIA. 



researches chiefly concerning Bursaria and Ophryoglena, have come into our 

 hands {A. N. H. 1856, xviii. p. 323). Since the introduction of it piecemeal 

 in our history of the organ would both have sacrificed its merits as an original 

 essay and have disturbed the continuity of our own account, we have deter- 

 mined to reproduce it here as a supplement. 



After describing the existence of two vesicles in Ophryoglena and Bursaria, 

 one near the mouth, the other situated jDosteriorly, he goes on to say that if 

 we examine a Bursaria fiava containing only the smallest forms of the 

 strongly refractive granules, " with a power of 300 diameters, we perceive 

 near the surface a quantity of light streaks, which run together towards the 

 contractile vesicle from the anterior and posterior parts of the body, in more 

 or less considerable curves. In each streak we detect an extremely delicate 

 but perfectly distinct canal, terminating ultimately in the contractile vesicle ; 

 its walls and its contents are readily distinguished by theii' different refrac- 

 tive power. When one of these canals is traced backwards from its orifice, 

 we may often perceive, after it has run a short distance, a ramification : this 

 may frequently be traced to one of the extremities of the body, and some- 

 times it gives off" another branch ; ultimately the canals become so excessively 

 fine that they are invisible. Their opening into the vesicle and their course 

 in running from it are seen very distinctly when the contractile vesicle is 

 turned dii-ectly upwards ; we may then recognize how the canals run between 

 the contractile reservoirs, which lie very close to the surface of the body, and 

 between the surfaces of the body inside the cortical substance ; and the ori- 

 fices may likewise be seen. Another remarkable position is when the nucleus 

 is turned next the observer at the surface of the body ; the canals are then 

 seen remarkably clearly on its bright background. A few canals always run 

 over directly, with a slight cui-vatm-e, towards the posterior part of the mouth. 

 "When the animalcule lies so that the contractile vesicle appears at the 

 margin of the body, there is sometimes an appearance as if one or more of 

 the canals opened externally at this point ; but close examination shows that 

 they ciuwe round and run towards other parts of the body. 



^' The number of vessels opening into the contractile vesicle in Bursaria 

 flava is about thirty ; this number, or a few more or less, existed in all the 

 specimens which I examined in reference to this point. They are apparently 

 imiformly distributed over the whole surface. 



^' The specimens of Bursaria flava with two contractile vesicles have the 

 system of canals double, each system grouped independently around its re- 

 servoir. The canals of the posterior reservoir stretch into the district of the 

 anterior ; but I have never been able to detect any communication between 

 the two. In the Ophryoglence from the Spree very httle could be detected 

 of the canals, even when the interior of the body contained only slightly re- 

 fractive substances. When a suitable sj)ecimen is somewhat compressed be- 

 tween the glasses, so that it cannot move about, the vessels are especially 

 seen when they have the nucleus for a background, and when they end in 

 the contractile vesicle. 



"' I have never been able to trace any vessels into the interior of the body 

 — for instance, towards the nucleus. I am also ignorant at present whether 

 that part of the contractile vesicle which is turned toward the centre of the 

 body of the animalcule receives any vessels. 



''Both Bursaria flava and Ophryoglena flavicans belong to those Infusoria 

 in which the contractile reservoii^s may assume the weU-lmown stellate form. 

 Yon Siebold describes this phenomenon in Paramecium in the following 

 words : — ' These pulsating spaces have a very striking shape ; they consist of 

 two central round cavities, around which stand from five to seven smaller 



