254 The Unity of the Organism 



to be known. When, consequently, the wliole complex is spoken 

 of as a "system of organs/' we must keep in mind the fact 

 that we are certain of its being a single system only in a 

 morphological sense. The mere fact that several organs are 

 structurally connected with one another does not by any means 

 signify that they are all concerned in a single operation. For 

 example, such complexes as muscle-nerve and gland-nerve-duct 

 are morphological systems which perform several quite distinct 

 functions. 



A matter of much theoretical interest is involved in the appli- 

 cation of the terms chromatic and chromatin to several of the 

 parts of the system. The karyosome of the nucleus is called 

 chromatin, as are the kinetonucleus, the basal granule, and the 

 granule in the axostyle near the posterior end of the body. And 

 the axostyle itself is said by Miss McCulloch to be "present ap- 

 parently in the form of a chromatic thread." The flagellum and 

 nuclear membrane are not held to be chromatic, even though 

 they seem to take stains quite as well as the other parts which 

 are called chromatin primarily because they are thus acted on. 

 Mention may be made too, of the fact that some of the parts, 

 notably the karyosome. w^hich are considered to be chromatin, 

 are shown by IVIiss McCulloch to stain with unequal intensity 

 at different times. The subject of chromatin and chromatic 

 bodies, has played a prodigious part in recent theoretical biology, 

 especially in speculations about heredity. We shall consequently 

 be obliged to give more attention to it in the discussion of how 

 organisms reproduce themselves. What has been described is 

 only the adult stage, or as it is often called, the vegetative stage 

 in the creature's life cycle, this being sufficient for our present 

 aims. Considerable is known about several other stages of 

 this and related species ; but our purpose now is only to get in 

 mind as clear a picture as possible of the make-up of the 

 animal in the culminating stage of its life. 



The other species selected to illustrate this new system of 

 internal protozoan organs shown in figure 9 is Giardia 

 muris, the specific name referring to the fact that the creature 

 is an inhabitant of mice. The figure and description are by 

 Kofoid and Christiansen. The facts to which special attention 

 is invited in this animal are the way in which all the various 

 granules and bodies are connected with one another by fibers, 

 the almost perfect bilateral symmetry of the animals, and 

 particularly the presence of two nuclei, nuc- The binuclear con- 



