1028 AQUATIC PHYCOMYCETES 



conidial Phycomycetes. 1 Gicklhorn's fungus is most certainly distinct 

 from Arnaudow's Bulgarian material. Then, too, Gicklhorn's Plate 2, 

 Figure F, presents structures which he regarded as "conidia," but which 

 most certainly are encysted zoospores, clumped, as in Sommerstorffia 

 and Aphanomyces, at the tip of a discharge tube projecting from the 

 carapace of the rotifer. It is possible, therefore, that there exist several 

 distinct fungi, alike in their vegetative stage and capturing organs, but 

 differing in their nonsexual reproductive structures. Which character 

 was typical of Sommerstorff's Z. insidians cannot now be determined 

 with certainty, although from his few remarks concerning this phase of 

 his fungus it is probable that zoospores were formed as they are in 

 Pythium. 



Interesting biological observations have been made on Zoophagus 

 insidians by Prowse (1954b). He succeeded in growing his material on 

 oatmeal agar, upon the surface of which was an abundance of water of 

 condensation, and discovered that under these circumstances only cer- 

 tain species of rotifers were captured. The fast-moving types escaped, 

 whereas the slow, browsing loricate types, such as Distyla, Monostyla, 

 and the like, were held and consumed. Soft-bodied ones like Rotifer, 

 however, may crawl over the trapping organs without being snared by 

 the device. 



Although zoosporangia were rare in Prowse's field material they were 

 abundant in his water cultures. In the latter the evacuation tubes reached 

 a length of 100 u, and from twenty to fifty zoospores, 10 by 5 (x (that is, 

 significantly larger than those of the wild specimens), were produced. 

 In the cultivated plants the capturing organs were lacking. When living 

 rotifers were introduced into the cultures, some of them were parasi- 

 tized. Since ingested zoospores, which are capable of infecting the animal, 

 were the only means of parasitism, the extent of predation by the fungus 

 was greatly reduced. All efforts to induce the cultured material to revert 

 to the field form with the peglike capturing organs failed. Further iso- 

 lations, and studies of a like nature of Zoophagus are desirable. 



1 The presence of gemmae in Arnaudow's Bulgarian material, in which zoospores 

 were also found, would seem, however, to argue against this. 



