06 



OUTLINES OF EVOLUTIONARY BIOLOGY 



theoretical reasons to postulate the existence of some such bodies 

 as Professor Weismann's biophors as the primary units of which 

 living protoplasm is built up. 



Then, again, although it may be questioned whether any 

 absolutely unnucleated organisms, such as Haeckel's Monera, 

 really exist, there can be no doubt that the most simply organized 

 living things known to us, the Bacteria, which probably stand a 

 long way below the point where the animal and vegetable king- 

 doms part company, and which are the most abundant of all 

 living organisms, do not show that sharp differentiation into 

 cell body and nucleus which is so characteristic of typical cells, 



FIG. 27. Bacillus saccobranchi. Bacteria from the Blood of a Fish (ftacco- 

 branchus) stained so as to show the distribution of the chromatin 

 (nuclear) material, which is represented in black, and which-may be 

 arranged in small scattered granules throughout the cell, or in an irregular 

 network, or in an irregular, more or less twisted rod, X 2000. (After 

 Dobell in the " Quarterly Journal of Microscopical Science.") 



the nuclear constituents being more or less scattered throughout 

 the cytoplasm (Fig. 27). 



A difficulty of another kind is met with in the fact that in a 

 good many cases the division of the nucleus is not followed at 

 any rate not immediately by corresponding division of the 

 cytoplasm. Some Amosbae constantly have two nuclei, and we some- 

 times get relatively large masses of protoplasm containing many 

 nuclei formed by repeated division. These are termed syncytia. 

 We meet, in fact, with all degrees of separation of the cytoplasm 

 into distinct cells, and a great many of the cells even of highly 

 developed plants and animals may remain connected together 

 throughout life by thin strands of protoplasm. We have already 

 noticed an example of this continuity of the protoplasm in the 



