$ 98. 
The first condition of every Echinoderm is the 
#ame, —an oval, ciliated body, resembling an in- 
fusorial animalcule, and without external organs, 
or distinction of parts. This is the starting-point, 
and upon it succeed variations according to the 
different families. Upon this ciliated body are 
developed, at one part, peduncles for its attachment 
to other bodies, while the rest of the germ increases 
in size, and assumes a star-fish form. 
The larve thus formed may be divided into two 
groups: 
1. Those of the Ophiuridae and Echinidae. 
2. Those of the Asteroidae and Holothuridae. 
The first’ are somewhat hemispherical bodies, 
qwith one edge of their truncated side prolonged 
into 4 single flat and wide process, which carries 
4the mouth and cesophagus ; while from the oppo- 
‘site extremity project rods, of four, eight or more 
in number, and which form the internal skeleton. 
See Ueb. d. Ophiurenlarven d. Adriat. Meeres. 
‘Taf.I. Il.) These larve have a globular stomach 
‘in their hemispherical portion, and from which pro- 
ceeds a short intestine terminating in a circular 
anus. They have, moreover, a ciliated fringe, 
which consists of a ridge covered with large cilia, 
passing above the mouth and before the arms, com- 
pletely encircling the body in an oblique manner. 
With the second group there is no internal cal- 
careous skeleton, and they form Miller’s Auricu- 
daria (of the Holothuridae), and Bipinnaria (of the 
Asteroidae). 
The first of these are concavo-convex bean- 
shaped bodies, with an irregular transverse fissure 
answering to the hilum of the bean, in which the 
‘mouth is placed. The margins of this fissure are 
ciliated ; the anus opens on the ventral surface. 
The Bipinnaria closely resemble these last, but 
they have a distinct ciliated circle in front of the 
mouth ; as they increase in size, the anterior part 
of their body is covered with long processes, which 
‘vary according to different forms. 
Out of these larvze, all of which have a strictly 
‘pilateral symmetry, the more or less radiate adult 
Echinoderms are developed by a process which is 
2 sort of internal gemmation. 
The changes and variations of this metamor- 
phosis I will give in Miilier’s own words : 
“1. The change of the bilateral larva into the 
Echinoderm takes place when the larva yet re- 
‘mains an embryo, and is universally covered with 
cilia, without a ciliated fringe. A part of the body 
of the larva takes on the form of the Echinoderm 3 
the rest is absorbed by the latter (a part of the 
Asteroidae, Echinaster, Asteracanthion, Sars). 
“9, The change of the bilateral larva into the 
Echinoderm takes place when the larva is perfectly 
g d; that is, p digestive organs and 
@ special ciliated fringe. 
THE ECHINODERMATA. 
99 
“The Echinoderm is constructed within the Plu- 
teus like a picture upon its canvas or a piece of 
embroidery in its frame, and then takes up into 
itself the digestive organs of the larva. Hereupon, 
the rest of the larva vani (Ophiura, Echinus), 
or is thrown off (Bipinnaria). 
“3. The larva changes twice. The first time it 
passes out of the bilateral type with lateral ciliated 
fringe into the radial type, and receives, instead of 
the previous ciliated fringe, new locomotive larval 
organs, the ciliated rings. Out of this pupa-condi- 
tion, the Echinoderm is developed, without any part 
being cast off (Holothuria, some Asteroidae). 
“Tf we call embryonic type the condition in 
which the animal leaves the egg, and when the 
internal organs are not yet developed, we have four 
stages or types, —the embryonic type, the larval 
type, the pupa type, and the Echinoderm type. 
The animal may pass from either of the first three 
forms into the Echinoderm, or may run through 
them all.” See Ueber. d. Larven u. d. Metamorph. 
d. Holoth. u. Aster. p. 33. See, also, a review of 
Miuiller’s researches, by Hualey (Ann. Nat. Hist. 
VII. 1851, p. 1), and by Dareste (Ann. d. Sc 
Nat. XVII."1852, p. 349). 
These results are highly interesting in both a 
zoological and a physiological point of view, and I 
need only suggest their important relations to the 
doctrine of “‘ alternation of generations.” 
In this connection, it may be proper to allude to 
another point. It is well known that Vogt (Na- 
turgesch. d. lebend, u. untergegang. Thiere. I. 
Liefer. 3, p. 254) has removed the Beroid Medusae 
from the Acalephae to the ‘Molluscoida,” re- 
garding them bilateral animals. In a private 
letter from Agassiz, there is a passage bearing 
directly on this point. He says: “The young 
Echinoderms are structurally and morphologically 
homologous with Beroid Medusae, showing that 
Beroids are genuine Radiates, and truly belong to 
the class of Acalephae, and cannot be referred to 
the Moll ids. These relations will be plain by 
comparing Taf. I. fig. 6, of Muller’s Larven und 
d. Metamorph. d. Ophiuren und Secigel. 1848, with 
the figures of Pl. VIII. of Agassiz’? Memoir on the 
Beroid Medusae, in the Mem. of the Amer. Acad. 
of Arts and Sc. Vol. IV.” 
For further writings on the development of the 
Echinoderms, see Muééer’s papers, published in 
his Arch. 1848, p. 113 ; 1849, p. 84, 364; 1851, p. 
1, 272, 353 ; but these papers gre all included in 
his large memoirs already given. See, also, Krohn, 
Beitrag. zur Entwickelungsgeschichte der Seeigle- 
larven, 1849, and in Miller’s Arch. 1851, p. 338, 
344, 368 ; and Desor, Miiller’s Arch. 1849, p. 79. 
— Ep. 
