Infusorial Circuit of Generations. 233 



once. Crawling and darting by an apparatus of marginal bristles, 

 prolonged in front and particularly in the rear, it is destitute of the 

 " propulsive vacuoles," as found, e. g. in the large " Paramecium 

 Aurelia ;" but besides being studded, particularly in the rear por- 

 tion, with a great number of larger and smaller granular ])ellets, 

 its body exhibits near the middle a large, clear, and granular 

 " germinal speck" or nuchiis, which is often observed to swell, 

 protruding globularly over the surface, below and above, when seen 

 crawling in profile.* 



Occasionally it is seen to extrude suddenly that turgid germinal 

 nucleus or yolk (vitellus), which, as in all these cases, is itself coat- 

 less, but hung around with divers jerking molecular fragments torn 

 loose from the parental body, which is rujyturecl on the s])ot, but 

 readily " re-cemented," as it were. 



The larger of these coatless granular yolks (constituting the 

 original j^seitrZo -genus, and species " Zoogloea Termo Dujard ") t 

 mostly consist of two parts, viz. a general " albumen " of a granular 

 and evidently trabecular texture, enclosing one or two distincthj 

 coated, quite hyaline and perfectly globular vesicles. The latter 

 resemble in shape a very clear white currant, as it were, by having 

 a sharply-defined circlet inscribed near one side, that is caused 

 by a local inversion of contents (somewhat like the air-vesicle 

 within a hen's egg). 



( Jb he continued.) 



* The transformation of the " rear-part " of Oxytricha, as given by J. Haimc 

 in 'Ann. Sci. Nat.,' Ser. 3, torn, xix., p. 109 (and represented in Carp. ' Micr.,' 

 pp. 447 and 448), I have not been able to verify myself; it must not, however, by 

 any means be confounded with the cncystments (1) of VorticeUa, producing wafer- 

 like molecules; (2) of the non-pulsating, tear-shaped "Paramecium kolpoda" 

 grub, producing free Oxytricha; nor (3) with that of the "oyster" or " porte- 

 monnaie " grub, producing paramecium-like bodies, Gregarina-fashion ; nor cither 

 (4), witli some large Oxytricha "currants," containing the revolving "crucible." 



t As represented by Cohn in 'Nov. Act. Nat. Curios,' 1854, vol. i., tab. xv., 

 fig. ix. In Klob's ' Microscopic Eesearches on Cholera ' the term is misapjdied to 

 engorged joints of dissected corruptive fibrils (or " Oidium lactis ") replete with 

 bacterial daughter-cells. 



