22, THE VOYAGE OF H.M.S. CHALLENGER. 
ones just beneath the calyx. Throughout its whole length it tapers downwards from 
the calyx, rapidly at first, then more slowly and afterwards somewhat rapidly again, 
till the joints are but little larger than those of the most developed cirri on its middle 
part. The number of internodal joints also diminishes in this lower part of the stem ; 
for while it reaches eleven or twelve in the middle of the stem, the numbers in the four 
lowest internodes are respectively nine, seven, five, five ; and the remains of the cirri borne 
at the intervening nodes show a corresponding diminution in size. The inferior termi- 
nation of the stem is not known, as it is broken at the syzygy beneath the lowest whorl 
of cirri. 
The free mode of life appears to be attained in these individuals, not by actual 
fracture of the stem at a node so as to shorten it more or less, but by the lower and 
therefore older part remaining undeveloped, while new joints appear in succession above 
it, each growing to a larger size than those previously formed. The stem thus becomes 
slender and tapering, and but ill adapted for attaching itself below; but its length 
is not diminished so much as if it were broken at a node. 
The downward tapering of the stem in some of the fossil Pelmatozoa has been 
already noticed; and it is evidently a character of more general occurrence than 
was suspected by Sir Wyville Thomson. Quenstedt’ contrasts the comparatively 
short tapering stems of Kxtracrinus briareus with the gigantic ones of Hatracrinus 
subangularis, which may reach the length of 50 or even of 70 feet; and he 
suggests that the former type and its allies “kénnten gleichsam als ee Comatula 
betrachtet werden, deren Knopf zu grésserer Liinge in einer Zeit heranwuchs, wo es 
noch keine eigentlichen Comateln gab.” De Loriol? in like manner regards it as 
probable—“ quwils avaient, & l'état adulte, une tige court, libre, et qu’d l’aide de leurs 
cirrhes tres nombreux et trés longs ils pouvaient nager facilement et se transporter, 
rapidement peut-étre, d’un lieu & un autre; ils avaient aussi la faculté de se fixer & 
quelque objet, lorsqwils en avaient le désir, au moyen des crochets dont est munie 
Vextrémité de leurs cirrhes.” 
I suspect, however, that the swimming was effected rather with the arms than with 
the cirri, which are not used for that purpose by the Comatule, and would have to 
be moved with considerable power in order to effect the locomotion of the animal. 
The condition of so many recent species is a strong argument in favour of the views 
formerly expressed by Buckland® and others regarding the possible locomotive powers 
of the Liassic Pentacrinide, though they have been somewhat discredited of late. Now 
too that their recent representatives have been found so abundantly in depths of less 
than 100 fathoms, instead of being exclusively abyssal types as was once supposed, the 
1 Encriniden, p. 271. 
2 Notice sur le Pentacrinus de Sennecey-le-Grand, Chalon-sur-Saone, 1878, p. 12. 
3 Geology and Mineralogy, vol. i.’p. 437. 
