472 On the Structure and Natural History of the VorticellEe. 



Fig. 3. The nucleus broken up into separate segments, as a further effect 

 of gemmiform conj ugation. 



Fig. 4. The segments of the nucleus {placenta, Stein), and in part also 

 the nucleoles contained in them, have escaped from the common 

 nuclear envelope, and are driven about freely in the body-cavity 

 of the Vorticella : 4 a, free larger nucleoles of the nuclear segments. 



Fig. 5. Epistylis mitiuta, sp. n. The whole stock shown magnified about 

 400 diameters. 



Fig. 6. Zoothamnium alternans (North Sea). 



Fig. 7. A single branch of Zoothamnium alternans with two small indivi- 

 duals, more highly magnified. 



Fig. 8. The conical base of the body of Carchesium 2}olgpinum seen from 

 below (in transverse section). The circles of granules indicate 

 the lumina of the muscles of the body and peduncle. 



Fig. 9. Representation of the course of the ciliary spiral in Carchesium 

 2)olypimim : s, commencement of the spiral ; the arrows indicate 

 the course of the spiral from the right of the buccal orifice to- 

 wards the left, to penetrate, after one circular tm-n (w), in a 

 curve into the vestibulum ; p, the outer peristome ; v, entrance 

 into the vestibulum (buccal orifice) ; g, the long seta projecting 

 from the vestibulum ; a, anus ; h, contractile vesicle ; r, the nou- 

 contractile receptacle, covered -with bacilli (see p. 462). 



Plate XV. 



I^g. 1. Epistylis flavicans, under a low power : r, rosettes of fissional 

 scions ; k, gemmiform conjugation. 



Fig. 2. The posterior extremity of the peduncle of Epistylis Jlavicans, 

 more highly magnified (300-400 diam.). 



Fig. 3. Epistylis Jlavicans seen from the point of junction with the pe- 

 duncle. The fibres radiating from the peduncle indicate the 

 longitudinal muscles, and the concentric circles the transverse 

 annulation of the skin. 



Fig, 4. Transverse section of the peduncle of Epistylis Jlavicans. 



Fig. 5. Epistylis Jlavicans, magnified 300 diam. : n, nucleus filled with 

 spermatozoid-like corpuscles ; k, paired capsules with roUed-up 

 threads in their interior (urticating capsules ?) situated under' 

 the skin ; g, the longitudinal fibres (muscles) and transverse 

 striae of the cuticula (compare fig. 3). 



Fig. 6. Isolated spermatozoid-like bodies from the nucleus of fig. 5, mag- 

 nified about 800 diam. 



Fig. 7. Isolated (m-ticating) capsules, more highly magnified : «, with the 

 threads rolled up in the interior ; b, with protruded threads. 



Fig. 8. The same, magnified about 300 diam. 



Fig. 9. A branch of Epistylis Jlavicans with two individuals, of which 

 the dark prominent nucleus is filled with spermatozoid-like 

 bodies. 



Figs. 10-14. Development of nucleoles (germ-granules) in the nucleus of 

 Epistylis Jlavicans. 



10. Nucleus filled with finely granular substance, in which no fur- 

 . ther form-constituents are recognizable. 



11. A clear longitudinal axis, still consisting of separate pieces, runs 

 through the middle of the nucleus. 



12. The longitudinal axis is continuous and filled with dark gra- 

 nular substance. 



13. Nucleiform structures issue from the longitudinal axis, finally 

 enveloping it. 



