942 REPORT — 1900. 



5. Observations on Pythium. By G. Poirault and E. J. Butler. 



The genus is of wide distributiou. being found cbiefly in the soil, but also ia 

 water Seven species were examined, two being undescribed forms. Two others, 

 P nracile Schenk, and P. iJitermecUmn, formed sexual organs hitherto unknown 

 in' these species. They are both parasites, the former in green algse, the latter m 

 the roots of a number of phanerogams, and are also both capable of saprophytic 

 life All forms are able to form sporanges and gonidia, some giving one sort of 

 spore more readily than the other. Klebs's results on the dependence of spore- 

 formation in Saprolegnia on external circumstances were carried a step further, 

 it being shown that a given spore could be induced to give zoospores or vegetative 

 hyphse''on appropriate treatment. _ . ■, , i r .i ^ j -u j u 



The process of zoospore-formation differs considerably from that described by 

 previous authors, being closely comparable to that of the Saprolegniacea. A 

 vacuole is formed in the discharging process, probably containing a cellulose- 

 alterino- enzyme and some chemiotactic substance whose function it is to draw out 

 the protoplasm from the sporange into the spore vesicle. The ripe sporange also 

 contains a motile vacuole which discharges to the exterior just before the escape 

 of the protoplasm. Septa are formed in all species. Pythium represents a stage 

 in the colonisation of the land by saprolegniaceous ancestors resembling Aphano- 

 myces. It is closely linked to the Peronosporacese through P. intermedium, 

 whieb possesses chains of gonidia, suckers, and a thick-walled resting mycelium. 



6. Observations on some Chytridinese. By G. Poirault and E. J. Butler. 

 Four undescribed forms occur parasitic on Pythium. Their life history has 



been worked out. » , , r xi. ^-e 



Chytridium gregarium, Nowakowski, was found on the eggs ot the rotiter 

 Metopidia Upadella. The unknown resting spores were discovered. 



Two observations were made on Olpidiopsis saprolegriKe. The infection takes 

 place in the zoospore stage of Saprolegnia, and is often multiple. Penetration 

 takes place by a tine tube through which the protoplasm of the parasitic zoospore 

 enters the host, leaving behind an empty capsule. 



A sort of diplanetism occurs in Olpidiopsis, the zoospore shedding its two cilia, 

 altering shape and acquiring two new cilia one after the other. 



The work was carried out chiefly at the Villa Thuret, Antibes. 



7. On the Azygospores of Entonioplithora gloeospora. 

 By Professor P. Vuillemin. 



The genus EntomopMliora, as seen in the two species E. Delpiniana and E. gloeo- 

 spora shows an intermediate condition between Sasidiobolus, with its uninucleatod 

 segments, and Empusa, with its continuous hyph;c with scattered nuclei ; for lu 

 Entomophthora the nuclei are large, and arranged at regular intervals m a single 

 row This state of things had led me to regard the non-septate condition as 

 arising from the failure to develop septa for the delimitation of the cytoplasmic 

 areas of the individual nuclei resulting from the division of a parent nucleus, and 

 to describe the condition as ' apocytial,' and the multinucleate mass of protoplasm 

 so formed as an ' apocyte ' or ' apocytium.' An exammation of the restmg-spores 

 alone found in Entomophthora has revealed the following history of their formation. 

 They may be terminal, lateral, or intercalary, and in the limbs of Mycetophila tbese 

 spores may be found of all ages, and arranged in basipetal succession of age, as 



shown by the increasing thickening of the wall from O'/o^ to 4,x, or even b-b^i. 



The youngest spores contain a single nucleus, which undergoes a series of four 

 successive binary divisions until there are 16 ; however, there may be irregulr.rities 

 so that the number may fall as low as 12, and in one case I have counted 

 as many as 17. In the next stage the nuclei approach so as to form eight pairs, 

 and the two nuclei of each pair then fuse : this fusion is repeated until at length 



