298 Mr Thomson on the Star-Fish of 



tualions, otherwise we should find them iiidiscriminately on fuci, 

 shells, stones, &c., which does not appear to be the case. How- 

 ever this may be, if we are allowed to assume that the Penta- 

 crinus europaeus is the young of comatula, we first perceive the 

 dispersed and attached ova in the form of a flattened oval disk, 

 by which it is permanently fixed to the spot Eelected, giving exit 

 to an obscurely jointed stem, ending in a club-shaped head, as 

 in Fig. 2, e, in which individual the animal is sufficiently advan- 

 ced to shew the incipient formation of the arms and the mouth 

 with its tentacula, by means of which it obtains the food neces- 

 sary to its successive growth. At d of the same figure is an- 

 other, somewhat more advanced, in which all the ossicula of the 

 arms are obvious, as far as the bifurcation. At the letters a, b and 

 c are represented, what I considered formerly as completel}/ form- 

 ed pentacrini, (a) from the position shewing the valvular mouth, 

 and (x) the anal aperture ; {li) shews most clearly the cirri or 

 claspers at the top of the stem, and (c) that the living principle 

 extends throughout the entire fabric demonstrated by the varied 

 movements of the pedicle. At a later period I observed indi- 

 viduals shewing a still higher degree of development, Fig. 4, and 

 in which the arms had the appearance of bifurcating twice to- 

 wards their extreme ends, and had become of a sulphur-yellow 

 colour, with a zone of dark coloured spots along either margin. 

 Another circumstance confirmatory of these being the young of 

 comatula is derived from these pentacrini being first seen about 

 the time of the dispersion of the ova of the comatulae, and again 

 entirely disappearing in September, the only season when young 

 comatulae are to be obtained, and such as are represented Fig. 5 

 and 6. In these the points of resemblance to advanced penta- 

 crini have been already alluded to, and it is quite evident, that 

 since they became detached, pinnae must have been added in 

 both directions, both towards the apex and downwards towards 

 the base of the arms. Those specimens which have made a further 

 progress are plentiful, and have all the pinnae complete down to 

 the bifurcation, with a few additional claspers added at the back. 

 At Fig. 7, a middle-sized Comatula decacnemos is given, as they 

 appear in June when pregnant with ova; and at Fig. 8 is a por- 

 tion of an arm magnified, with the ova beginning to escape from 

 the conccptacula, which they do successively from the base up- 



