CHYTRIDIALES 473 



dissolving fluid if they are to maintain themselves in such a substratum. 1 

 It is obvious that the "fossil" nature and affinities of these forms must 

 await the results of investigation on living material, which no doubt 

 exists. Such investigation will be difficult because of the opaque nature 

 of the substratum. 



These shell-boring "fungi" have been known for a long time, and in 

 1860 Kolliker (1860a, 1860b) issued an extensive account of various 

 "vegetable parasites" of shells, sponge spicules, scales of fishes, and the 

 like. In Kolliker' s paper are references to still earlier investigations. As 

 a result of his studies he concluded that the extraneous structures were 

 fungi and noted that they were very frequent in marine organisms and 

 almost or wholly lacking in fresh-water forms. He also noted that not 

 all marine animals were prey to the parasites, those with chitinous 

 material are free of them. In the Mollusca, on the other hand, uninfected 

 shells were the exception. Types with a thick periostracum and a pris- 

 matic layer were not attacked, the fungi evidently not being able to 

 effect penetration. The shell-boring forms apparently accomplished their 

 entrance by the secretion of an acid which dissolved the lime or, in the 

 resistant sponge skeletons, possibly by mechanical action. Kolliker left 

 open the question of whether they were algae or fungi, but was strongly 

 inclined toward believing that they belonged to the latter group. 

 Other fossil chytrids have been described by Daugherty (1941). 



Opportunity was also afforded for examining sponge spicules with nu- 

 merous canals in them. These were kindly sent by Dr. Arndt of the 

 Berlin Zoological Museum. As in the shell-boring "Cladochytria," 

 however, nothing could be definitely learned from prepared material 

 concerning the affinities of these organisms. Until all of them have been 

 studied in the living state and their spore structure determined little can 

 be said of their relationships to the chytrids or, indeed, to the fungi. 



1 Other slides kindly sent by Mr. Zebrowski show cavities shaped exactly like 

 certain monocentric chytrids such as Asterophlyctis. 



