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ON THE ORIGIN AND METAMORPHO SES OF |. As this process continues the little creature gradually 
NATURE | 107 
loses its power of swimming and sinks to the bottom, 
; : INSECTS * loses the bands and cilia and attaches itself to some 
r Vv. stone or other solid substance, by its base, the knob of 
‘THE development of the beautiful Comatula rosacea the club being free. The calcareous framework increases 
y _ (Fig. 41) has been described in the “ Philosophical | in size, and the expanded head forms itself into a cup, 
; ions,” by Prof. Wyville Thomson,” The larva quits round which from five to fifteen delicate tentacles, as 
‘ shown in Fig. 44, make their appearance. 
In this stage the young animal resembles the Crinoids, 
a family of Echinoderms which were very abundant in 
earlier geological periods, but which have now almost 
disappeared, being, as we see, represented by the young 
states of our existing, more advanced, species. This 
attached, plant-like condition of Comatula, was indeed at 
Fic. 41.—Comatula rosacea (after Forbes). 
___ the egg, as shown in Fig. 42, in the form of an oval body 
__ about 34; inch in length, something like a small barrel, 
! surrounded by four bands or hoops of long vibratile hairs 
or ciliz, There is also a still longer tuft of hairs at the 
narrower posterior end of the body. Gradually a number 
of minute calcareous spines and plates make their appear- 
ance (Fig. 43) in the body of this flarva, and at length 
ee ate 
7 
a | 
,@ 
’ \ Fic. 42.—Larva of Comatula rosacea (after Thomson). 43, Larva of Coma- 
. a tula rosacea, more advanced. 44, Larva of Comatula rosacea, in the 
Pentacrinus state. 
first supposed to be a Crinoid, and was named Pentacrinus, 
though we now know that it is only a stage in the deve- 
lopment of Comatula. The so-called Pentacrinus in- 
creases considerably in size, and after various gradual 
changes, which time does not now permit me to describe, 
quits the stalk, and becomes a free Comatula. 
The metamorphoses of the true star-fishes are also very 
remarkable. Sars discovered in the year 1835 a curious 
little creature about an inch in length, which he named 
Bipinnaria asterigera, and which he then supposed to be 
allied to the ciliograde Medusz ; subsequent observations 
however, made in 1844, suggested to him that it was the 
Fic. 45.—Larva of Starfish (Bipinnaria), x 100 (after Muller). 46, Larva of 
Starfish (Bipinnaria), x 100, seen from the side, a, mouth ; 4, cesopha- 
us: ¢, stomach: c*, intestine. 47, Larva of another Bipinnaria, 
ywing the commencement of the starfish. g, canal of the ciliated sac; 
#, rudiments of tentacles; d, ciliated band. 
arrange themselves in a definite order, so as to form a 
bent calcareous club or rod with an enlarged head. 
* Continued from p. 70. 
t Philosophical Transactions, 186s, vol. cly, . 513. 
