42 BIOLOGY OF THE PROTOZOA 



with an accumulation of carmine granules where three planes of 

 contiguous bubbles come together, while the spaces within the 

 meshes w^ould be filled with air. The apparent network, however, 

 is merely the optical section of continuous walls of bubbles enclosed 

 on all sides by the water and soap. The physical structure of the 

 protoplasm of a few Protozoa, called spumoid structure by Rhumbler 

 ma,y be accurately compared with such an emulsion of soap and 

 water. An analogous network, usually of exquisite fineness, rep- 

 resents the more solid substance of protoplasm; the apparent fibers 

 forming the meshwork in some cases at least are the optical sections 

 of continuous walls, which, like the soap bubbles, enclose materials 

 of lesser density. Biitschli, who with Rhumbler, has studied the 

 finer structure of protoplasm of lower plants and animals as well 

 as that of higher forms, was the first to compare such structures 

 with the alveolar structure of emulsions like soap and water, oils 

 and water, etc. The granules of protoplasm, corresponding in 

 position with the carmine of the soap suds, lie in the substance of 

 the denser network of interalveolar material to which Dofiein 

 applies the term stereoplasm. The alveolar sul)stance, called rheo- 

 plasm by Dofiein, corresponds in position with the air of the soap 

 bubbles. 



All who have investigated protoplasm agree that it is not a homo- 

 geneous substance but a mixture of colloidal substances in the 

 physical state described l)y Ostwald as an emulsoid in which the 

 interalveolar materials act in the manner of a dispersing agent while 

 the more fluid intra-alveolar substances are dispersed, but all are 

 subject to reversal of phase. 



While the alveolar structure of protoplasm is convincingly demon- 

 strated by a number of typical forms of living Protozoa, this struc- 

 ture is difficult to make out in other types. Thus in the endoplasm 

 of flagellates like Chiloinonas, or the endoplasm of Actinophrys sol, 

 or ActinosphoBrium eichhornii, the alveoli are easily discernible, 

 but in Paramecium caudatuvi, in many gregarines, and in many 

 types of flagellates and ciliates, the alveoli, if present, are too fine 

 to be seen with the usual powers of the microscope. Vonwiller 

 (1918) can find no evidence for upholding the alveolar theory of 

 protoplasmic structure in general. 



Certainh- in many cases the protoplasm appears to be almost 

 homogeneous in structure, the granules alone being e^'idence of 

 structural configuration. Such forms are illustrations of the gran- 

 ula theory of Altmann, who held that protoplasm is made up of a 

 congeries of such granules or microsomes each of which is termed a 

 bioblast, each bioblast being regarded as a single unit performing 

 all of the functions of living matter including growth and reproduc- 

 tion. Here, however, theoretical considerations have been super- 

 imposed on the obvious structures and the physical appearances 



