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 (Opalina 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 . 



the most improved methods of staining (Myxomycetes). 



FIG. 19. -ladopho.a, glomer 

 ata. A cell from a thread in a 

 chromic acid carmine prepara- 

 tion (after Strasburger, Proct. 

 Botany, Fig- 75): n nucleus; 

 ch chromatophores ; p amyloid 

 bodies (pyrenoids) ; o starch 

 granules (x 540). 



