218 Barrett, — Development and Sexuality of some 
plasm has become more dense and contains many small granules along with 
the increased number of oil bodies (Figs. 17, 78). At this time there is 
a marked radiating condition of the host protoplasm which decreases 
rapidly in extent as the sporangial development proceeds (Figs. 17, 18, 79, 
80). Vacuoles of rather indefinite outline now appear in the parasite 
(Figs. 18, 81), which soon round up into one or several nearly perfect spheres. 
The protoplasm is now dense and granular. The large oil or fat-like bodies 
have disappeared. The sporangium is now said to be ripe and may enter 
directly into the maturation stages or undergo a limited period of rest 
before zoospore formation takes place (Fig. 82). I have observed sporangia 
remain in this condition for several weeks without losing their power 
of zoospore formation (Fig. 19). The only necessary condition, according 
to my observations, to start up the internal changes which bring about the 
discharge of zoospores is that fresh water and oxygen be supplied. 
Maturation. Concerning the maturation stages of P seudolpidium 
Aphanomyces , Butler ( 4 ) has given a detailed account. The changes which 
take place in the ripe sporangium of the Olpidiopsis species concerned, just 
previous to zoospore production, agree in the main with those described for 
the above species. I find, however, that the minute details in the behaviour 
of the protoplasm vary somewhat with the different sporangia of the same 
species. 
Soon after the proper conditions are supplied to the ripe resting 
sporangium, one observes a change in the contour of the prominent spherical 
vacuoles. Usually the exit tubes begin to develop at this time and the 
protoplasm has the appearance of already being segmented (Figs. 14, 
82). No heapings of the protoplasm such as described by Butler for 
P. Aphanomyces were seen to take place at this time. In a short 
time the vacuoles suddenly disappear, when the protoplasm presents 
a rather fine granular, homogeneous, and lighter appearance. It is at this 
stage, according to Butler, that the first shaping of the spore origins in the 
sporangium of P. Aphanomyces occurs. After a few minutes there may 
or may not appear a number of smaller spherical vacuoles surrounded by 
the now denser protoplasm. 
After fifteen to thirty minutes the vacuoles disappear and the proto- 
plasm becomes more coarsely granular. The zoospores take on a more 
definite outline and their movement increases. Suddenly the exit tube 
opens and their escape takes place. 
The number and length of the exit tubes vary with the different 
species. In O. luxurians they usually number one or two, and extend 
some distance beyond the host wall (Fig. 16). In O. Saprolegniae the 
number of exit tubes is small, one to three, and they are comparatively 
short. In O. vexans they are usually more numerous, often numbering as 
many as six. Fig. 20 shows a sporangium of 0 , vexans which rested after 
