ACIII.^\ 121 



diclinous antheridia, longer oogonial stalks, smaller aMiayf luinilicr of 

 ci;jis and uniiittcd oo.uonial walls (oxcvpt wlu'it' the antheridia toiirli). 

 With Pieters's descri|)tion our plant agrees unusually well and the 

 idcntit\- of our plants is olnious. Neither on flies nor on termites do we 

 fmd a jironounced tendency to produce all the oogonia near the insect (as 

 rieters tinds in the case of his form on flies), and on corn meal agar our form 

 produces copious oogonia and antheridia with normal t'ggs. Pieters 

 says that oogonia were not formed on the agar he used fcorn nu-al agar 

 not mentioned). In fact, he found oogonia to he formed only on flies 

 and in one case on a sterilized pea. The oogonia are not ^•ery densely 

 set and, while more numerous near the substratum, occur throughout 

 the culture except for a peripheral zone where the sporangia are being 

 formed. The species is a very strong and rapid grower, is healthy and 

 riliable in ordinary media and forms oogonia regularly. At room 

 temperature a culture made on a fly at i p. m. was discharging spores 

 at 6 p. m. the following day. On corn meal agar in a petri dish at room 

 temperature (65-75° F.) the growth is at the rate of nearly a centimeter 

 a day. When sporangia discharge in agar they do so only in part and 

 the spores are forced back in a sheath around the sporangium just as is 

 shown for A. flageUata (plate 37, fig. 12). .Six cultures made to test the 

 effect of low temperature showed that in the ice box (about 10-11° C.) 

 in all cases oogonia were formed in immen.se quantities throughout the 

 culture, while sporangia were very rare. In check cultures at room 

 temperature there were produced large numbers of sporangia and far less 

 numerous oogonia. 



The spores vary in behavior as usual in the genus; Acry often only 

 a part emerge and not rarely all are retained. \\'hcn the spores escape 

 t>pically they emerge from their cysts and swim as usual, but some or 

 all of them are not rarely seen to sprout in position. There is a strong 

 tendency in this species for the spores to emerge from more than one 

 mouth; (for other such cases see A. Carolinian a, A. proliferoides and A. 

 flagellata). .Sporangia with multiple mouths are of constant occurrence 

 and are not to be confused with dictiosporangia (see fig. 6). In such cases 

 some of the spores are nearh' always left inside. One remarkable condition 

 was seen .scores of times and has not appeared so strikingly in any other 

 Achlya. The retained spores emerged from their cysts inside the spor- 

 angium and swam \ery acti\ely inside it, none ever getting out even 

 though the opening was free. In a number of cases in which nearly 

 all the spores were retained they beha\ed in this way and the sporangia 

 presented a novel sight with hundreds of spores swimming rapidlj- in a 

 crowded swarm. In such cases the empty cysts were soon dissolved, leaving 

 the space free. After coming to rest inside the sporangium many of these 



