ITS CHEM1CO-PHYSICAL AND MORPHOLOGICAL PROPERTIES 



39 



cells of the spinal cord, extremely large vesicular nuclei are seen. 

 Similarly, enormously large nuclei occur in immature egg-cells, 

 which themselves are of a great size. Sometimes the nuclei of 

 immature eggs of Fishes, Amphibians, and Reptiles are perceptible 

 to the naked eye as small spots ; 'under these circumstances they 

 can be easily extracted with needles and isolated. Yet there are 

 exceptions to this rule ; for even these same eggs which, when 

 immature, have such immense nuclei, 

 when they are mature and fertilised 

 contain such minute nuclei, that they 

 can only be demonstrated with the 

 greatest difficulty. 



The lowest organisms, when of a con- 

 siderable size, frequently possess one 

 single large nucleus. It is sometimes 

 enormously large in the central capsules 

 of many Radiolarians. 



As regards the number present, as a 

 general rale there is only one nucleus in 

 each cell in plants and animals. To this 

 rule, however, there are some exceptions ; 

 there are frequently two nuclei in liver 

 cells, whilst a hundred or more have 

 been observed in the giant cells of bone 

 marrow. Osteoclasts and the cells of 

 many tumours, the cells of several Fungi, 

 and of many of the lower plants, such as 

 Cladophora (Fig. 19) and Siphonese (Bo- 

 try dium, Vaucheria, Caulerpa, etc.), are 

 remarkable for this plurality of nuclei, 

 as has been described by Schmitz. 



Similarly, a large number of the 

 lowest organisms, such as Myxomycetes, 

 many Mono- and Poly-thalamia, Radio- 

 larians, and Infusoria (OpaMna ranarum\ 

 possess many nuclei in each cell. Fre- 

 quently in these cases the nuclei are so 

 minute, and are distributed in such 

 numbers throughout the protoplasm, 

 that they have only been demonstrated quite recently by means of 

 the most improved methods of staining (Myxomycetes). 



FIG. 19. dadophor 

 ata. A cell from a thread in a 

 chromic acid carmine prepara- 

 tion (after Strasburger, Pract. 

 Botany, Fig. 75) : n nucleus ; 

 ch chromatophores ; p amyloid 

 bodies (pyrenoids) ; a starch 

 granules ( x 540). 



