796 AQUATIC PHYCOMYCETES 



fertilization always takes place if antheridia are present has been a 

 matter of considerable discussion in the past (Coker, 1923; Fitzpatrick, 

 1930). The male gamete is never flagellate and, like the female, never 

 makes contact with the outside medium. 1 



The mature oospore is surrounded by a thick wall. The contents 

 consist of a finely granular matrix within which are formed, typically, 

 numerous small fatty droplets which surround wholly or in part a single 

 large globule or several smaller ones. The structure of the egg in the 

 Saprolegniaceae is of considerable taxonomic importance. According 

 to Coker (1923: 10), there are two main types: 



In all cases the fatty reserve is on or near the periphery, but in one type it 

 is in the form of small droplets entirely surrounding the protoplasm, while in 

 the other it is collected into one or a few larger drops on one side. The first 

 of these types is called centric, the second eccentric, but intergrading types 

 occur which connect the two extremes, and for certain of these I have found 

 it useful to introduce the word subcentric. The three terms may be defined 

 as follows: 



A centric egg has one or two layers of small fat droplets entirely surrounding 

 the central protoplasm. 



A subcentric egg has the protoplasm surrounded by one layer of droplets 

 on one side and two or three layers on the other, or rarely with the droplets 

 entirely lacking on part of one side as wxAchlyu oblongata; this last condition 

 connecting directly with such eccentric structure as is shown by Pythiopsis 

 cymosa. 2 



An eccentric egg has one large drop on one side either outside the proto- 

 plasmic surface or barely enclosed by a thin layer of protoplasm, or several 

 large drops enclosed in the protoplasm on one side, or a lunate row of small 

 drops (in optical sections) on one side, as in Pythiopsis cymosa. 



After a period of rest the oospore germinates to produce a tube which 

 either elongates and reestablishes the thallus or forms a sporangium at 



1 Apinis (1935) described as Archilegnia latrica, a saprolegniaceous fungus in which 

 the eggs are said to be fertilized by minute uniflagellate free-swimming male gametes. 

 As has been pointed out by Coker and Matthews (1937), recognition of such an 

 aberrant organism must be withheld until a further study is made. From the figures 

 given, it is entirely possible that the material carried a persistent monad infection. 



2 Johnson (1956) has recognized three types of subcentric eggs in Achlya: I, with 

 one layer of small oil droplets on one side of the ooplasm and two or three on the 

 opposing side; II, as in Type I but with the single layer of droplets not formed, thus 

 giving a lunate grouping of droplets partially surrounding the ooplasm; III. with a 

 singlj circular layer of small droplets located eccentrically to the oospore wall. 



