146 THE SAPROLEGNIACEAE 



by its deep penetration and destruction of the skin tissues [Hautge- 

 webe]. The fungus is always accompanied by bacteria, which are 

 probably symbiotic with it and help destroy the tissue. However, it 

 must not be overlooked that the same bacteria and other Saprolegniaceae 

 may occur on the same fish near A. Hojeri and not cause destruction 

 of tissue. Achlya Hojeri probably secretes an enzyme which attacks 

 the tissue and permits the penetration of the fungus threads and bac- 

 teria. 



"The assistant at the station. Dr. Plehn, reported to the author 

 as follows on the effects on the tissue caused by the disease: 



'After the fungus gets a foothold on the surface it soon begins to 

 penetrate deeper, but proceeds only slowly. Only after weeks is the 

 epidermis [Oberhaut] penetrated. In an infected carp that had been 

 observed for months the fungus had penetrated the entire dermis [Unter- 

 haut], occupying, however, only the fatty connective tissue and stop- 

 ping at the muscles. In the deeper tissues also indeed in the dermis, 

 the fungus is not dense, and one sees in very old infections only isolated 

 threads, which mostly follow the cavities of the tissue and run between 

 the harder layers of the dermis. Strangely there is an absence of in- 

 flammation in the neighborhood of the fungus. The greater and more 

 serious disorganization that sometimes occurs in this infection, when 

 even the muscles are involved, is due to other causes — the myriads of 

 bacteria that are present.' 



"Achlya Hojeri is near A. oligacantha deBary. It is distinguished 

 from the latter by the entire absence of antheridia, the more elongated 

 and larger oogonia, the mostly larger and more numerous spores [mean- 

 ing oospores probably]. 



"Occurs so far only on Bohemian mirror carp in February of this 

 year. The inoculation was successful in the case of three carp at the 

 Biological Station, Munich." 



One good text figure on page 366 shows oogonia and blunt tipped 

 sporangia much larger than the hyphae. The spines as shown are not 

 sharp. A very peculiar species. 



EXCLUDED OR DOUBTFUL SPECIES NOT MENTIONED IN THE TEXT 



Achlya leucosperma Cornu. Ann. Soc. Nat., Series 5, 15: 24. 1872. 



This has not been sufficiently described to make its position certain. It was dis- 

 tinguished from other species, especially ^. prolifera, by having only two pits in the oogonium 

 wall, white (not brown) eggs, and cylindrical antheridia which stand in a row on the ends 

 of the antheridial branches. These characters seem quite worthless and it is surprising 

 that Cornu should have so defined a species. It may be A. prolifera. All eggs of water 

 molds look milk-white when seen under reflected light. 



