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THE POPULAR SCIENCE MONTHLY. 



animalcules only after they were dead, that is, at the moment when 

 they had become globular and motionless, like protococci ; and his 

 specimens were dead, because he had filled his vials up to the brim 

 with the water, and then sealed them hermetically. But these little 

 animals must, above all things, have free respiration. Accumulated 

 in immense numbers in a very small quantity of water, with the outer 

 air entirely excluded, they all died while being carried from Villeneuve 

 to Montpellier. They were then taken for protococci, being motionless 

 and globular. I took precautions against committing this mistake, by 

 only half filling my specimen-tubes, and, better still, by examining the 

 water of the salines on the spot. 



Fig. 7. 



Aetemia Salina (adult) natural size, and highly magnified, o. Median eye. y, y. Pedunculate 

 eyes, a, e. Antennae, p. Incubatory pouch with eggs. ab. Abdomen, ap. Tail-shaped ap- 

 pendages, c. Digestive tube. 



It is a remarkable fact in the history of the Monas Dunalii that, 

 like the Protococcus nivalis, which gives to the snow of the polar re- 

 gions now a green tinge, anon a red, this animalcule presents, when 

 young, a green tinge, which changes later to brick-red, and then to 

 blood-red. 



