File:The royal natural history (1893) (14779065474).jpg

Identifier: royalnaturalhist612lyde (find matches)
Title: The royal natural history
Year: 1893 (1890s)
Authors: Lydekker, Richard, 1849-1915 Sclater, Philip Lutley, 1829-1913 Frostick, W. B., former owner. DSI Brooks, W. T., former owner. DSI
Subjects: Zoology Natural history
Publisher: London and New York : Frederick Warne & Co.
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Smithsonian Libraries

View Book Page: Book Viewer
About This Book: Catalog Entry
View All Images: All Images From Book
Click here to view book online to see this illustration in context in a browseable online version of this book.

Text Appearing Before Image:
widens into a stomach, and afresh mouth-opening (m) is pierced through atits upper end. This is seen from the side instage 4, and from the front in stage 5. Butbefore the mouth is formed, two ear-like pro-cesses (w) show themselves, which are importantas bein the beginnings of the ambulacral andwater-vascular systems. There also appear afew delicate, symmetrically laced rods of car-bonate of lime, which by and by grow into theskeleton of the larva, in shape something likean inverted easel. The two lower ciliated DE VEL OPMENT. 1 ? bands now grow towards one another, so that the vent comes to lie beneaththem (stages 7 and 8). They also join themselves to the two upper bands, sothat there is formed a single zone of cilia, which persists to the end of thelarvas life. Already can be distinguished the beginnings of the apex and of theprocesses (e), which finally lengthen into the arms that give such a strangeappearance to the larva, in the sea-urchins and also in the star-fish and brittle-
Text Appearing After Image:
DEVELOPMENT OF A SEA-URCHIN (stage 10). stars. In stage 8 can be seen, at b, the pore that admits water to the water-vascular system; and at this point will lie the madreporite of the future sea-urchins. The next illustration shows all these parts in a rather more advancedstage : a is the vent; c, the hinder intestine ; (/, the stomach, around which a depositof spicules indicates the first beginnings of the body of thevsea-urchin; o, the gullet;on, the mouth; e, the arms of the larva: r, the calcareous rods that support them : v,two more strongly-developed and slightly projecting portions of the ciliated band :and w, the water-vessels. The larva in its full development is shown in the 3i8 E CHINODERMS. illustration on p. 317, in which the letters have the same meaning. This larvalform is called a Platens, on account of its frequent changes of shape, as it swimsabout with its arms constantly moving. It will be noticed that through the wholeof its development it retains a two-sided symm

Note About Images