Philodinaea.} T HE INFUSORIA. 401 



presence of an animal so complicated, living as a parasite 

 in the cells of an utricular aerial tissue, is a phenomenon 

 of the most curious kind in the physiology of plants, and 

 the more so as this animal is an aquatic one. 



"I recollected that the last year of my residence in Flan- 

 ders, I found, near Ghent, the Vaucheria clavata, in which 

 I observed something similar. M. Unger had already 

 published the following details respecting this plant in 

 1828 : ' Beneath the emptied tubercles, and at several 

 points of the principal stalk, at different angles, rather 

 narrower branches are produced ; these branches are gene- 

 rally very long, and greatly exceed the principal stalk in 

 length. At the end of ten or twelve days after their 

 development, there are seen, towards one or the other of 

 their extremities, here and there, at different distances 

 from the summit, protuberances of a clavate form, more or 

 less regular, straight, or slightly bent back ; and others on 

 the sides of the stalk, which have the form of a capsule, or 

 vesicle. These vesicles are, at first, of a uniform bright green 

 colour, and without increase of size, which exceeds several 

 times that of the branches ; they always become of a 

 blackish-green colour, darker towards the base, and then 

 one or two globules, of a reddish-brown, may be clearly 

 distinguished there, often surrounded by smaller granules, 

 evidently destitute of motion, whilst the great ones move 

 spontaneously and slowly, here and there, in the interior 

 of the capsule, by unequal contractions and dilatations, 

 whence arise remarkable changes of form. I saw these 

 globules at the end of eight or ten days after their appear- 

 ance, still inclosed in the capsule, moving more and more 

 slowly, receiving no very decided increase, whilst the base 



