Natural History of the Infusoria. 333 



two and four parts, but the nucleus could not be traced durin<^ 

 this process. The investing membrane fell to pieces, and the 

 little spheres, which may perhaps be regarded as four quiescent 

 spores, were no more to be seen (PL XL figs. 22, 23). 



Whether another circumstance observed by me has any con- 

 nexion with the reproduction of Difflugia, must be ascertained 

 hereafter. In all the individuals of Difflugia contained in one 

 vessel, the substance of the body became converted into granules 

 closely packed together (fig. 24), the form and the investing 

 membrane being retained. I often saw these granules in quick 

 molecular movement in the interior of a sac, which appeared to 

 be formed from the outermost layer of the body, but 1 watched 

 in vain for any issue to this ; after moving for about half an hour, 

 the granules always became quiescent again. 



If we bring together the results of this investigation, it ap- 

 pears that — 



1. Difflugia Enchelys has a nucleus. 



2. As other Rhizopoda, Amoeba for example, also possess one, 

 a nucleus probably occurs in all Rhizopoda. 



3. Difflugia Enchelys propagates by gemmation. 



4. It is probable that other Rhizopoda also propagate by 

 gemmation. 



5. Difflugia Enchelys forms four quiescent spores. 



EXPLANATION OF PLATE XL 



Fig. L Polytoma Uvella, magnified 300 times: — a, the starch-like gra- 

 nules; b, the nucleus with its nucleolus; c, the contractile 

 vesicles. 



Fig. 2. The same after long action of chromic acid. 



Fig. 3. The same bisected. 



Fig. 4. The commencement of the constriction for quadrisection. The 

 direction of the constriction of the other half lies in the plane of 

 the paper. 



Fig. 5. The quadrisection completed. 



Fig. 6. The divisions have acquired the oval form. 



Fig. 7. Quiescent state : — h, nucleus. 



Fig. 8. The investing membrane divided into granules. 



Fig. 9. Another mode of quadrisection. The portions have nearly acquired 

 the oval form before quadrisection. 



Fig. 10. Position of the fully-developed young in this mode of division. 



Fig. 11. The two halves have slightly changed their position before qua- 

 drisection. 



Fig. 12. Position of the young in this mode of division. The two lower 

 ones lie across the upper, and appear through them. 



Fig. 13. The body occupying only one side of the investing membrane. 



Fig. 14. The body is contracted into the hinder portion of the membrane, 

 and only connected with the filaments by a thin thread. 



F^g. 15. The filaments contracted into two little knobs. 



Figs. 16, 17, 18, 19. Different forms of Difflugia Enchelys, 



Fig. 20. Adherent specimens of Difflugia. 



