423 



mouiitaius. coueluded that the beetle had carried the alg;^. Later he ex- 

 amined six beetles belouging to three species, from five different habitats 

 and found attached to them twenty-three species of algse. 



These ciliates and algge, however, were attached to beetles in the water. 

 When the beetles leave the water these attached organisms are suddenly 

 transferred from an aquatic to an jprial environment. This new envii'on- 

 ment differs from the old one in temperature and humidity. How long 

 these organisms can resist these changed conditions and how long the 

 b^tles stay out of water are facts that must be known before the role of 

 insects in the distribution of attached organisms can be accurately deter- 

 mined. The fact that aquatic beetles fly at night reduces the harmful effect 

 of e^■aporation. Experiments are planned to solve these problems. 



In the notes on Episti/Iifi, I have indicated that that species of this 

 genus can i»main out of water for some time without fatal results. The 

 colony leferred to remained on a slide under cover in a room with low 

 relative huu}idity for more tlian fifteen hours without it being fatal to all 

 of the zooids. While a colony of this species attached to the thorax of a 

 beetle making a nocturnal migratory flight would not have the protection 

 against evaporation of the two glass plates, this would be compensated 

 in some degree by the more humid and cooler night air. 



That wind is responsible for the distribution of many protozoa and 

 rotifers is a fact wlilch is familiar to any one who has ever made a hay 

 infusion. The presence of these organisms and of tardigrada in the pond, 

 is probably due to wind distribution. Just how far an organism can be 

 transported by wind depends upon the size and specific gravity of its spores, 

 eggs or cysts, and upon its power to resist drying, extreme temperature, 

 etc. These facts are, in a large number of cases, unknown. 



Cysts of Euglena are common in almost every culture, but it does not 

 follow that this Is the form in which they are wind-blo-^m. Assuming a 

 constant specific gravity, it is certain that the buoyancy of a cyst increases 

 as the reciprocal of its diameter. As an adaptation to this law, many 

 oi'ganisms form extremely minute spores. 



It is rendered very probable by Calkins ("07) that in Amceha protcus 

 very minute spores are formed. From his figures I have determined the 

 diameter of the tertiary nuclei (wliicli with a bit of cj^toplasm are pre- 

 sumed to form the spore), to lie 1 n or less. Coriiparing these spore nuclei 

 in Calkins ("07), Fig. 14. with the amceba figured in his earlier papers. 



