PROPAGATION or CEETAIN ECniNOBERMS. 59 



trivial ambulacra and the ambulacra of the bivium, are con- 

 siderably wider than the other three ; cousequently, in a trans- 

 verse section, the ambulacral vessels do not correspond with the 

 angles of a regular pentagon, but with those of an irregular figure 

 in which three angles are approximated beneath and two above. 

 In the female the tentacular parts of the dorsal (bivial) ambulacra 

 are very short ; they are provided with sucking-disks ; but the cal- 

 careous support of the suckers is very rudimentary, and the 

 tubular processes are not apparently fitted for locomotion. In 

 the males there is not so great a difference in character between 

 the ambulacra of the trivium and those of the bivium ; but the 

 tentacles of the latter seem to be less fully developed in both 

 sexes, and I have never happened to see an individual of either 

 sex progressing upon, or adhering by, the water- feet of the dorsal 

 canals. 



In a very large proportion of the females which I examined, 

 young were closely packed in two continuous fringes, adhering to 

 the water-feet of the dorsal ambulacra (fig. 1). The young were in 

 all the later stages of growth, and of all sizes from 5 up to 40 

 millims. in length ; but all the young attached to one female 

 appeared to be nearly of the same age and size. Some of the 

 mothers with older families had a most grotesque appearance — 

 their bodies entirely hidden by the couple of rows, of a dozen 

 or so each, of yellow vesicles like ripe yellow plums rauged along 

 their backs, each surmounted by its expanded crown of oral ten- 

 tacles ; in the figure the young are represented as about half- 

 grown. All the young I examined were miniatures of their 

 parents ; the only marked diff'erence was that in the young the 

 ambulacra of the bivium were quite rudimentary, they were 

 externally represented only by bands of a somewhat darker orange 

 than the rest of the surface, and by lines of low papillae in the 

 young of larger growth ; the radial vessels could be well seen 

 through the transparent body-wall ; the young attached them- 

 selves by the tentacular feet of the trivial ambulacra, which are 

 early and fully developed. 



We were too late at the Falklands (January 23) to see the 

 process of the attachment of the young in their nursery, even if 

 we could have arranged to keep specimens alive under observation. 

 There can be little doubt that, according to the analogy of the 

 class, the eggs are impregnated either in the ovarial tube or im- 

 mediately after their extrusion, that the first developmental 



