PROGRESS IN CYTOLOGY 173 



commissioned by him to make an investigation into the 

 problem of the sexuality or non-sexuality of the Ascomy- 

 cetes. Strasburger, it should be remembered, was at 

 the time more or less a convert to Brefeld's views. Harper, 

 who, like a certain Israelitish prophet, had been brought 

 to " curse the house of " De Bary ended in " blessing it 

 altogether/' for he was able to prove that some of the 

 simpler Ascomycetes at all events were certainly possessed 

 of sexuality, and of course if any single genuine Ascomycete 

 could be shown to possess sexuality Brefeld's phylogeny 

 at once fell to the ground. Many British botanists, 

 however, remained staunch supporters of De Bary's 

 views, and the publication of Harper's work fully justified 

 their conservatism. 



The period 1870-90 saw also the complete establish- 

 ment of the symbiotic theory of the structure of the lichen 

 thallus, and of the correctness of Schwendener's views 

 on the subject. As in the case of the Algae, much special 

 research was carried out on individual genera and on 

 specific questions concerned with the fertilisation of the 

 Saprolegniae and other Phycomycetes, as also on the 

 Schizophyta and the animal-like Mycetozoa, but into the 

 discussion of these researches I cannot enter. 



PROGRESS IN CYTOLOGY 



You will remember that in the years between 1850 

 and 1860 the whole outlook in vegetable, and indeed also 

 in animal, anatomy and histology underwent a complete 

 change owing to the establishment of the cell theory by 

 Schwann and Schleiden, and owing to the identification 

 of protoplasm as the essential constituent of the cell. 

 The years that followed were rich in research on the new 

 structural and physiological problems opened up by these 

 two great generalisations. The investigations were con- 

 cerned chiefly with (i) the minute structure and chemical 

 composition of protoplasm ; (2) the structure of the nucleus 

 and its behaviour during cell division ; (3) the structure and 



