PVTillOPSIS 19 



comes obscured and the oogonium seems to he seated at maturity on a 

 large, swollen, basal cell, lender high power, however, the original 

 septum may be seen as a somewhat thicker disc. This form of anther- 

 idium, as shown in fig. i and in one of the two in fig. 2, is not exactly 

 illustrated in either deBary's or Humphrey's figures. From this strictly 

 basal and closely pressed antheridium we ha\'e in the remaining half 

 of the oogonia all sorts of variations. The antheridium may be ele- 

 vated on a stalk that varies from nothing to half the length of the oogo- 

 nium and in very rare cases the antheridium may be even of diclinous 

 origin (figs. 5 and 6). The appearance of several antheridia on one 

 oogonium is of rather frequent occurrence in our cultures. This is not 

 recorded by deBary or Humphrey. From figures 3 to 7 an idea may 

 be gained of the variations observable in both antheridia and oogonia. 

 DeBary does not give the size of the eggs. We find them to vary from 

 14.8 to 24^1, with an average of about 19. Six. This is a little larger than 

 the figures given by Humphrey. 



The remarkable intercalary oogonium shown in fig. 8 is unique. 

 Its single egg was 27.8 by 50[i. in size and a large number of oil drops 

 were grouped at each end. An antheridial cell was also cut ofif at each 

 end, but no antheridium could be made out. 



The peculiar jelly-like outer layer that deBary noticed on the oogonia 

 in October cultures w'as also seen by Humphrey in a few cases. By 

 careful observation we have been able to make out this layer in the ma- 

 jority of young oogonia. It is probably present on all at a certain stage, 

 but in clean cultures free from bacteria is very hard to trace. Its pres- 

 ence and outline is hardly discernible, except for the bacteria and other 

 minute particles that stick to it. As remarked by Humphrey, it is hardly 

 possible that this hyaline gelatinous outer sheath can be a "periplasm" 

 secreted from the oogonium contents, as deBary suggests. It is more 

 apt to be due to the gelatinization of a thin outer layer of the wall of 

 the oogonium. 



In a typical clean culture in spring water on a mushroom grub the 

 sporangia varied from 37 to 56:0. in diameter, the majority being from 

 44 to 48,A broad. 



In figures 9 and 10 are shown sporangia of usual appearance. When 

 the sporangia proceed at once to the formation of spores the discharge 

 is usually at the tip (fig. 9). If a rest occurs, the immergence tube is 

 as apt to appear at the base, as shown in fig. 11. After the first sudden 

 release of pressure the spores do not rush out as in Achlya and Sapro- 

 legnia, but emerge much more quietly as they find the opening. The 

 last ones often swim around a long time in the sporangium before finding 

 an exit. The spores are pear-shaped, with two cilia at the small end. 



