An Investigation of a Species of Saprolegnia. 309 
and Adilya in cases where the sporocysts fail to discharge their 
zoospores. In this case encystmeut takes place within the 
sporocyst. The spores may later be discharged in the second 
motile stage, or they may germinate in situ without any such 
motile stage. In either case such a sporocyst is known as a 
“ Dictyosporocyst.” 
Special Characteristics of Saprolegnia. 
Certain phenomena may now be specially referred to, which 
are characteristic of large sections of the Saprolegniaceae and 
which have been employed in the effort to establish a system of 
genera upon the asexual reproductive characters. 
Diplanetism .—This term is applied to describe the occurrence 
of two motile stages in certain species and genera. The two forms 
of zoospore are different. The first form of zoospore is ovoid with 
two terminal equal flagella. The second form is slightly kidney 
shaped, with two unequal lateral flagella. Both forms have one or 
more contractile vacuoles. The second form of zoospore resembles 
that which is characteristic of the Peronosporeae. 
Adelphotaxy — A term used to describe the mutual attraction 
for each other, sometimes shown by the zoospores when at close 
quarters. This is exhibited in the case of Adilya and yet more 
strongly in the genera in which no discharge of the zoospores 
takes place. It is also held accountable for collection of the swarm 
spores into clusters. 
The formation of gouidia. —Gonidia, resting sporocysts or 
gemmae occur in some species of Saprolegnia , Adilya and 
Aphanomyces. They resemble the first stage in the development 
of the sporocyst after the formation of the septum and they are 
able to remain for a long period without change. On germination 
they may either develop vegetative hyphae or they may develop 
into normal sporocysts. In many cases they become completely 
separated from the hyphae on which they were formed. 
The formation of dilamydospores. — Chlamydospores closely 
resemble gemmae or resting sporocysts, but they produce on ger¬ 
mination a hypha, which terminates in a sporocyst, or, in some 
cases, a secondary gemma. 
