140 The Microscope. 



fullest development in ordinary cases until after the third moult. 

 Several foreign warblers have similiar plates appended to the crest, 

 breast, and throat-feathers in other colors, but I have not yet been 

 ^ble to examine them critically. It is a field that I shall hold in 

 reserve until opportunity offers, unless I find it already pre- 

 ■empted and occupied. 



CYTOLOGY, OR CELLULAR BIOLOGY. 



HISTORY OF THE SCIENCE — SECOND PERIOD — CONT'd. 



V. GENERAL CONSTITUTION OF THE CELL AND SOME NEW 



DEFINITIONS, 



REV. A. M. KIRSCH, C. S. C, 



PROFESSOR OF BIOLOGY, UNIVERSITY NOTRE DAME. 



NOT only was the character of protoplasm studied during this 

 period, but the general constitution of the cell was also made 

 ihe subject of special researches. Among others, we find se- 

 pecially von Mohl, for a period of twenty years, edited an unin- 

 terrupted series of masterly publications, in which he sets forth 

 not only the internal organization of the vegetable world, but 

 also the general structure of the cell, and more particularly its 

 minute organization, which no one before had even suspected to 

 ■exist. Von Mohl studied particularly the solid membrane and 

 ihe plastic membrane, the distribution of the protoplasm in the 

 interior of the cell, the nature of the inclusions, the chemical 

 ■composition of the membrane, the albuminous nature of proto- 

 plasm, thus elucidating so many points in the study of the cell, 

 that he may be justly styled the father of Cytology. From this 

 the reader may see that von Mohl justly merited the eulogy of 

 Henstein, who thus speaks of him in an article on protoplasm, 

 published in the Revue Internationale. Oct. 15th., 1880: " It was 

 reserved to Hugo von Mohl to elucidate the subject of the ele- 

 mentary structure of the cells of plants in its most ingenious 

 rsimplicity. Not only did he lay the first true foundations of our 

 iictual knowledge upon this subject, but he exposed clearly its 

 most important traits." 



In 1844, von Mohl called attention to an essential point, 

 namely, the differentiation of the peripheral layer of protoplasm. 

 He showed that this layer is modified and transformed into a 

 thin lamella, which he calk utricle or primordial membrane. 



