222 Ml'. H.J. Carter on the Organization of Infusoria, 



opposite (fig. 79) . In Amceba Gleichenii the nucleus itself oc- 

 casionally presents a pellucid spot or punctum in its centre. 



In Vorticella there is a long cylindrical organ, which appears 

 analogous to, if not homologous with, the nucleus, and this, in 

 a large Epistjjlis common here, and some other species of Vorti- 

 cella, is wrapped once round the upper part of the buccal cavity, in 

 the same manner as the ovary is wrapped round the visceral organs 

 of Salpa among the Tunicata (fig. 74^). Stein states that after 

 Vorticella microstoma has become encysted, this organ divides 

 up into embryos, which, when the parent integument bursts, 

 come forth like " Monas colpoda or Monas scintillans " ; and he 

 '^ assumes " that these monads, after having become fixed and 

 stalked, pass into young Vorticellae* ; — an assumption which can 

 hardly be doubted, though it may be some time before chance 

 favours its demonstration. 



In Otostoma, and many forms of Ehrenberg's Enterodelous 

 class of animalcules, there is a similar organ, either of a cir- 

 cular, cylindrical, or fusiform, elongated shape (Annals, vol. xvii, 

 pi. 9, fig. 6). In Oxytricha also there is something of the kind, 

 and in Himantophorus {Charon, Ehr., mihi) it extends nearly all 

 round the body, commencing from the posterior extremity, and 

 terminating on the right side close to the vesicula. 



The cylindrical organ in Vorticella not unfrequently presents 

 a granular appearance, and the granules, which are minute, but 

 uniform in size, appear to occupy the periphery ; but whether 

 they are inside or outside the wall of the cylinder, or in the sub- 

 stance of the wall itself, I have not been able to determine. 

 Stein places them inside, in the form of a granular cylinder, and 

 within this " nucleoli f/' — nucleated, discoid bodies, into which 

 the nucleus becomes divided. 



In the Rhizopodous cell which inhabits the protoplasm of the 

 CharaceceX, it is at first uniformly clear and transparent, then 

 semi-opake and subgranular, afterwards two or more distinct 

 granules make their appearance, and finally it becomes wholly 

 granular and much enlarged; or undergoes fissiparation and 

 thus gives origin to more cells, like the cytoblast of the vege- 

 table kingdom. 



Use. — It is impossible, in the present state of our knowledge, 

 to specify the uses of the nucleus. One point, however, is evi- 

 dent, that it appears very early in the development of the freshv 

 water Rhizopoda, sponge-cell, &c.; and another, that it bears a 

 close analogy to a similar organ in the vegetable cell, viz. the 



* Ann. and Mag. Nat. Hist. vol. ix. p. 4/4 & HI. 



t Die Infusionsthiere, &o. Taf. 4. fig. 24. 4to, Leipzig, 1854. 



X Ann. and Mag. Nat. Hist. vol. xvii. p. 101, 1856. 



