154 THE LOWER FUNGI— PHYCOMYCETES 



fertilization occurs. De Bary, failing to note the discharge of 

 the content of the tube into the oosphere, was the first to question 

 it. He studied living material of several species of Saprolegnia, 

 and concluded that even in those cases in which the fertiUzation 

 tubes reach the oospheres they fail to rupture and fertilize them. 

 Parthenogenesis was believed by him to be usual in the group, 

 and his views have subsequently been maintained by various 

 students including Marshall Ward, Hartog, and Davis. The 

 early work on the problem was done on living material. Conse- 

 quently the study of nuclear phenomena was impossible, and 

 the actual fusion of sex nuclei could not be demonstrated. Later, 

 with the advent of modern cytological technique, various workers 

 have sought to solve the problem of sexuality in the group. 

 Unfortunately the results have been diverse, and a bitter contro- 

 versy has ensued. 



Trow has published several papers in which he claims to have 

 demonstrated a true fertilization and a fusion of sexual nuclei 

 in several species of Achlya and Saprolegnia. His statements 

 have been severely attacked by Hartog and later by Davis, both 

 of whom are firm in the conviction that parthenogenesis is 

 present throughout the group. Consequently, our knowledge 

 of the sexuality of these forms is in a state of uncertainty. The 

 papers of Hartog (1896; 1899), Trow (1895; 1899; 1904), and 

 Davis (1903) afford interesting reading on account of the fre- 

 quently caustic criticisms which they contain. The fact that 

 in cytological investigation interpretation plays an important 

 role is well illustrated by the work on this group. 



The oogonium of the Saprolegniaceae in the young condition 

 is multinucleate. When the oospheres round up they also are 

 multinucleate, the number of nuclei in the oogonium greatly 

 exceeding the number of oospheres formed. The oospheres at 

 maturity are, however, uninucleate. To explain the disappear- 

 ance of the remainder of the nuclei two theories have been 

 advanced. Hartog maintains that nuclear fusions many times 

 repeated reduce the number until only one nucleus remains in 

 each oosphere. Trow and Davis believe that the supernumerary 

 nuclei degenerate. Occasionally fully formed oospheres are 

 found to be binucleate. Hartog considers such cases as merely 

 the last stage in the general nuclear fusion. Davis feels that 

 they represent those instances in which two nuclei happen to lie 

 near a coenocentrum, and are thus both saved from degeneration. 



