238 BULLETIN OF THE UNIVERSITY OF WISCONSIN. 



into stomata vera and pseudo-stomata. Stomata vera are small 

 openings at the junction of several epithelial cells. They are 

 said to be bounded by small cells in the process of division — 

 the so-called "germinating cells." "These cells when ripe be- 

 come detached and may at once be absorbed as lymph corpuscles" 

 (sic). 



The character of pseudo-stomata they describe as follows : 

 "There exist superficial branched cells in the serous membranes 

 which lie either totally or partially between the endothelium of the 

 surface, or, as is more commonly the case, only reach the surface 

 by a process which projects between the superficial endothelium. 

 * * * * we shall show * * * what great importance must be 

 ascribed to these freely projecting cell processes; we call them pseudo- 

 stomata." 



These cell processes by budding give rise to single cells, and 

 in certain pathological conditions cell proliferation takes place 

 from them. Klein also makes the statement that "in female 

 frogs, during the spawning season, the endothelial cells lining 

 the stomata are ciliated" ; a statement which I can not support 

 and have not found corroborated by anyone. 



Although the subject has received much attention from in- 

 vestigators there still exists a great diversity of opinion as to 

 what are, and what, are not, stomata; or, to put it differently, 

 what are pre-formed natural openings and what are artificial. 

 Even those authors who express a belief in the existence of 

 stomata do not do so in an unqualified manner. 



In general, stomata may be designated as small gaps or open- 

 ings in the intercellular substance of serous membranes. Some 

 investigators assert that these openings are pre — others that they 

 are post — embryonic formations ; while still others maintain 

 that they are accidental. 



One obstacle in the way of some definite conclusion is the fact 

 that investigations have been made on different animals, or at 

 least different parts of the same animal, under different condi- 

 tions, by different methods, and with conflicting results. An- 

 other obstacle is that some investigations have been carried on 

 to prove a preconceived idea and authors have read into every 



