190 ON THE SAPROLEGNIE^. 



The sporangia are terminal, and the zoospores are primordial 

 cells. Oogonia polysporous and terminal. 



2. — AcHLYA. In Achlya the sporangia are lateral, and the 

 new sporangia are also developed laterally from beneath the 

 septum. The zoospores are the products of a number of special 

 mother-cells, formed in the sporangium from its contents. 

 Oogonia polysporous. 



3. — Aphanomyces. The sporangia are thinner and more 

 elongated than in the other genera, and the zoospores are in 

 single file within them. Oogonia monosporous. 



4. — Pythium. The sporangia are inflated at the extremity 

 into a bladder, in which protoplasm collects, and from which the 

 zoospores are developed. Oogonia monosporous and not quite 

 terminal, being often surmounted by a little cylindrical portion of 

 the filament. 



5. — Leptomitus. The sporangia consists of pouches not 

 partitioned off, but furnished here and there with constrictions; 

 otherwise it corresponds very much with Saprolegnia. 



6. — MoNOBLEPHARis. The filaments of this genus are re- 

 markable, in that they give no reaction with sulphuric acid and 

 iodine, showing the absence of cellulose. The antherozoids are 

 formed in small spore-cases, which burst and allow them to dis- 

 perse through the water. 



It is a curious fact in the history of parasitism that the Sapro- 

 legftiea, which are themselves essentially parasitical, should in their 

 turn be the subjects of a parasitic growth, in the shape of a very 

 minute fungus belonging to the group Chytridincce. This group is 

 very probably allied to the Myxojiiycetes, for there are several 

 remarkable properties common to both — viz., the well-marked 

 resemblance of the zoospores to some forms of the Infusoria, the 

 amoeboid-movement, and the existence of a plasmodium, which 

 only becomes surrounded with a membrane at the epoch of repro- 

 duction. These minute parasites were observed by Pringsheim, and 

 described by him in his work on Achlya prolif era as sexual organs 

 of the Saproleguiae ; but Cornu, in an exhaustive monograph on 

 the subject, has shown their true nature. Among the reasons he 

 assigns to justify this opinion are : — The analogy of the bodies with 

 Chytridinece^ already known, and especially the identical form of 



