298 GENERAL HISTOliY OF THE INFUSORIA. 



these central almost fluid contents, two portions are distinguishable — ^one 

 occurring as a stream moving around the animalcule, within and upon the 

 cortical lamina, the other as a thinner central medium, apparently quiescent, 

 and in direct communication with the siuTounding water through the channel 

 of the ahmentary tube and mouth. To the first only of these two portions 

 Lachmann's term ' chyme ' is rightly applicable, since it no doubt represents 

 the nutritive material di^a"WTi fi'om the alimentary matters swallowed, and to 

 the elaboration of which the watery fluid of the centre most likely contributes. 

 Both portions contain food-vesicles, granules, and molecules ; but the former 

 possesses them in much greater abundance. When an animalcule dies, the 

 central contents are the first to escape, streaming forth from the mouth as a 

 diffluent film with granules and molecules imbedded in it ; a similar discharge 

 and " diffluence " also ensue when the protecting envelopes are torn through, 

 and the more so when some pressui^e is at the same time exerted. 



The following quotation from Lachmann elucidates veiy well several points 

 concerning the contents of the body in general. '' \\Tien," he writes {op. cit. 

 p. 126), " an Infusorium is sucked out by an Acineta, the cortical layer or 

 parenchyma of the body may often contract for a long time, and the con- 

 tractile vesicle placed in it may also continue its contractions for hom^s ; nay, 

 I have observed a Stijlonycliia, which, although a considerable part of its 

 chyme had been sucked out of it by an Acineta, still underwent division, so 

 that one of the gemmules of division swam away from it briskly, and only 

 the other half of the old animal was destroyed. This appears also, to a cer- 

 tain extent, to prove that the mass sucked out does not represent the time 

 parenchyma of the body ; and as it only fills the large cavity of the body in 

 the form of a tenacious fluid mass, and becomes mixed with the nutritive 

 matters, especially when no small masses are formed, it is certainly the most 

 natm^al course to regard it as chyme. It cannot be urged against this view, 

 that in those Infusoria which contain clilorophy 11- corpuscles in the substance 

 of their bodies, we sometimes meet \\ith single corpuscles in the rotating 

 mass, as they may certainly be easily loosened from the parenchyma, and 

 thus get into the chyme-mass. The nucleus, indeed, projects into the chyme- 

 mass ; but as a general rule it appears to be affixed to the parenchyma of 

 the body, as we do not see it rotate with the chyme-mass : in Opercidaria 

 herherina, Stein sometimes saw the nucleus moved a httle out of its previous 

 position by a mass of food striking against it ; but as it soon retm^ned again 

 to its position, this rather speaks for than against its attachment." 



Imbedded ^vithin the cortical layer a collection of remarkable structui'es is 

 discoverable in many species — for instance, in Paramecium, Oj^hi^yoglena, and 

 Bursaria — known under the name of thread- cells or trichocysts (XXXI. 1-4). 

 We are indebted to Prof. AUman for the minute and complete examination of 

 these bodies (J. M. S. 1855, iii. p. 177). He behoves it was these structures 

 which Cohn represented (as mentioned in a previous page) to be exceedingly 

 long cilia, and which Stein, in criticising Cohn's account, affirms to be cilia of 

 ordinary length, but appearing abnormally lengthened under external circum- 

 stances, such as the addition of strong acetic acid. Prof. Allman's description 

 is the best we have : — 



"When Bursaria leucas is examined under a sufficiently high power, 

 minute fusiform bodies may be detected thickly imbedded in its walls. 

 These bodies are perfectly colouiiess and transparent ; they ai^e about the 

 -gJL-th of an inch long, and may easily, even without any manipulation, be 

 ^dtnessed at the margin, where they are seen to be arranged perpendicularly 

 to the outhne of the animalcule, while on the siuface turned towards the 

 observer the extreme transparency and want of colour render them inrisible 



