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spring of that year. In 1910, Microspora flourished before 

 either Conferva or Oedogonium. Enough bas been said to 

 demonstrate the existence of such compétition and, altbougb it 

 is not always possible to say what is cause and wbat effect, tins 

 struggle between the différent gênera obviously plays a part in 

 determining iVequency during tlie spring-inonths. 



We bave thus arrived at a plausible explanation for tbe wide 

 séparation of tbe two maxima of Microspora in Mardi and 

 July of 1907; but for the compétition of Conferva and Oedo- 

 gonium the March-maximum migbt hâve continued uninter- 

 rupted to tbe July-maximum. Such a long-continued maximum 

 we see in tbe first five montbs of 1908. Howis it to be accoun- 

 ted for? We bave seen that Oedogonium was not a competitor 

 during tbis period, so tbat tbere was only Conferva to be 

 reckoned with. January 1908 was peculiar in having tbe lowest 

 average minimum and mean températures recorded during the 

 wbole period of observation. Thèse conditions may hâve given 

 such an impulse to the development of tbe Microspora that it 

 was able to persist throughout subséquent montbs, not presen- 

 ting such favourable meteorological conditions. It must be 

 noticed furtber tbat Mardi and April of 1908 were colder tban is 

 the rule and tbat Mardi shows the unusual phenomenon of pre- 

 senting lower températures tban February. It is therefore 

 évident that tbere are sufficiently peculiar température-condi- 

 tions in tbe first montbs of 1908 to give some explanation for 

 tbe prolonged maximum of Microspora. 



Tbere are certain features in tbe frequency table of Micro- 

 spora however that at présent appear to be quite inexplicable. 

 Tbe most puzzling of thèse is the diminution of the genus after 

 December 1906 and its recrudescence in Mardi 1907. Meteoro- 

 logical data and compétition afford no explanation whatever, in 

 fact the March-maximum occurs on a rising température and 

 under compétition with Oedogonium favoured by unusual 

 sunshine. It can therefore only be supposed that conditions of 

 which we bave no knowledge were responsible. The subséquent 

 periodicity of Microspora up to July of 1907 bas already been 

 fully considered. The decrease after July is no doubt due to 

 tbe graduai drying up of the pond. The decrease in June 1908 

 after the long maximum already considered corresponds to the 

 exceptionally warm May and June. 



We consider that the data given above indicate a marked 



