A4 THE WORLD OF THE SEA. 
The M/yrionema, a parasite which grows on the surface of other 
algze in small brown patches, and the Haligenia, whose extended 
frond is almost twelve feet in diameter, are reproduced by similar 
zoospores, which are both very small and both possess the same 
simple organisation. Analogy would lead us to suppose that 
the immense tree-like Lessonza of the Southern Ocean was pro- 
pagated by zoospores whose length was scarcely g,/ooth of an inch. 
Some sea-weeds have the property of producing zoospores in 
FORMATION AND EMISSION OF ZOOSPORES, 
(Bryopsis hynoides.) 
all parts of their tissue; in others this production is confined to 
certain parts of the fronds. The corpuscles always seem to be 
produced by a species of coagulation of matter contained in 
the cellules. This matter coalesces with grains more or less 
numerous; at first indistinct (fig. 1), then they become well 
defined (fig. 2), and at last the zoospores separate (fig. 3). The 
emission of the zoospores nearly always takes place by force, 
which is due to the expansion of the mucilaginous liquid with 
which the cellules are filled. 
This liquid accumulates gradually by endosmose, and at last 
ruptures the walls. As soon as they are free (fig. Z), the zoospores 
