252 ON THE PRESENT STATE OF OUR 



these I sliall first consider the most important points of their morphol- 

 ogy and anatomy, and afterward their classification. 



We will begin with the alga?. The reform in their study was inau- 

 gurated by two works which appeared almost simultaneously, Kiitzing's 

 Fhycologia universalis and Niigeli's latest algJB systems. Kiitzing pre- 

 sents a view of his organographic and anatomical studies, and bases 

 upon them a new system of alga?, illustrating it by means of j^lates. 

 The Species Algarum and the Tabula' phycologica'^ containing a description 

 and picture of all species of alga?, may be considered as supplements 

 to his great work. Kiitzing, no doubt, had greater facilities for the 

 study of alga? than almost any other investigator. He was the first to 

 examine the separate organs and the structure of fuci, and to found 

 this branch of phycology. lie broke up the classification of the old 

 genera, which contained a chaotic mass of the most different forms, 

 and separated them into natural groups. Unfortunately, Kiitzing re- 

 jected the usual nomenclature, and employed one of his own, thus mak- 

 ing his work very difficult to understand. In his classification he splits 

 up his material into too many untenable species, making it almost im- 

 possible to examine the whole. 



Niigeli exerted a no less important influence on the study of the al- 

 gte. In his algiie systems and in his work on one-celled algae, this 

 renowned anatomist shows his unsurpassed acuteness of observation in 

 his description of the structure and mode of life of those small organ- 

 isms which cannot be recognized with the unaided eye. He showedthat 

 the increase of the separated cells depends upon malihematically determ- 

 inable laws. These he developed for many species, and we may say that 

 he created a sure mathematical basis for the study of the algoe. Since 

 laws, valid in the whole vegetable kingdom, can be educed most easily 

 from the alga?, the simplest organisms, Niigeli's researches are of great 

 value to the whole science of botany. Starting from his discovered 

 principles, Niigeli planned an algce system of his own ; but here he was 

 less successful. 



Beside these two principal works, a great number of large and small 

 dissertations have been published. Among these the following are 

 the most important: The works of Alexander Brauu on the life and 

 devel()i)inent of microscopic forms, are worthy of being placed side by side 

 with those of Nageli. In them, and especially in the classical work on 

 rejuvenation in the vegetable kingdom, he has produced real master- 

 pieces of short but very attractively written monographs, calculated to 

 excite the interest of every man of culture. Professor Cohu, another emi- 

 nent scholar, has given to the world a series of masterly and thorough 

 essays on the Volvociiuc, which had until then been classed as animals. 

 De Barry's dissertation on the Conjugates does not fall short of the other 

 essays. 



The brilliant discovery of the zoospores of algae was made by Pro- 

 fessor Unger, who observed the formation oli these movable cells in 



