274 THE SEA-WEEDS AT HOME AND ABROAD. 
Fig. 9. Pterygotus bilobus. 
Fig. 10. Terminal tail joint of Prerygotus acuminatus. 
Fig. 11. The smaller one is Limulus just hatched, natural size, mere out- 
line; the larger is the same undergoing the first moult, and leaving 
the old shell, and having a tail. 
Fig. 12. Limulus Polyphemus, one year old. The markings on the pos- 
terior carapace become less distinct with adult age. The adult female 
will attain a size even exceeding twelve inches across the cephalic 
hield. 
Fig. 13. Eurypterus remipes ; size very much reduced. 
Fig. 14. Sao hirsutus, a trilobite. 
THE SEA-WEEDS AT HOME AND ABROAD. 
BY JOHN L. RUSSELL. 
Tue vegetable productions of the ocean, like those of the 
drier portions of the earth, are subject to'a similar order of 
distribution. The most common collector of plants becomes 
soon aware that there are kinds which are not to be looked 
for in ordinary places, and soon learns to set a value on those 
which rarely occur to him. He also desires to extend. the 
area of his observations so as to embrace different latitudes, 
orío obtain the same results by ascending lofty mountain 
heights. So the collector of sea-weeds does not confine 
himself to particular districts, but endeavors, either by per- 
sonal inspection or else through the labor and courtesy of 
others, to ascertain what forms, seemingly familiar or entirely 
diverse, may grow abroad. The deeper soundings of the 
ocean-beds, like the higher elevations of the land, afford him 
a greater variety, affected by different causes, which in their 
natural course produce different results. — 
The general plan of vegetable life, especially in the lower 
plants, seems to point to constant modification of some one 
typical form, and this modification appears to have its origin 
in climatic influences. It becomes a most fascinating study 
to endeavor to join the separate and divided links so as to 
