Aug., 1891. 
CRINOIDS. 
181 
Fig. 17.—A Tadpole shortly after the time of appearance of the 
limbs: the hind limbs are seen at the junction of the body and 
tail: the fore limbs are present but are concealed by the opercular 
folds covering the gills. At this stage the Tadpole breathes by both 
gills and lungs. X 1. 
Fig. 18.—A young Frog with the tail only partially absorbed. 
x 1. 
Figs 19 to 22.—Stages in the development of the West Indian 
Frog, Hylodes: illustrating the effect of increased amount of food yolk 
in causing the omission of ancestral stages. The free living tadpole 
stage of the common Frog is entirely suppressed, and no gills are ever 
formed. The entire development from the laying of the eggs to the 
hatching of the Frogs occupies from a fortnight to three weeks. (After 
Brehm.) 
Fig. 19.—The larva at the end of the first week. The head, eyes, 
stumps of the limbs, and the long tail are well shown. The food yolk 
is contained within the large yolk-sac in the middle of the figure. The 
figure should be compared with Figs. 15 and 16, which are drawn to the 
same scale. X 3. 
Fig. 20.—The young Hylodes shortly before hatching. There is 
still a very large tail present which is believed to be used as a respi¬ 
ratory organ. X 3. 
Fig. 21.—Young Hylodes at the moment of emerging from the egg: 
a short stump of a tail is still present. X 3. 
Fig. 22.—Young Hylodes at the end of the first day. The tail is 
completely absorbed, and the Frog has already the form of the adult. 
x 3. 
ON CRINOIDS. # 
BY W. MADELEY, 
HON. SEC. OF THE DUDLEY AND MIDLAND GEOLOGICAL SOCIETY. 
It is not at all surprising that those early naturalists, who 
directed their attention to the examination of the fossil 
crinoids, should have considered them to be the petrified 
remains of some marvellous creations of the vegetable king¬ 
dom ; and it is uncertain by whom or when the name of 
Encrinus (from the Greek word Kpivov, a lily) was first applied, 
but we find that Agricola, in Ins “ De re metallica,” published 
in 1558, speaks of them under this name, and also applies the 
name of Trochites (wlieel-stones) to the separated ossicles of 
the stem. The Encrinus liliiformis from the Muschelkalk 
beds of Germany was for a long time considered the type of 
the class, and is still figured generally in geological manuals 
as a typical fossil of those beds. The name of Encrinus has 
been retained for the genus to which it was originally applied, 
and the name of Pentacrinus, by which Agricola distinguished 
* Read before the Birmingham Natural History and Microscopical 
Society, December 16th, 1890. 
