REPORT ON THE ASTEROIDEA. 187 
spreading a little way along the arms and on the dorsal surface of the disk; the young 
escape from the marsupium chiefly in the neighbourhood of the angles between the 
rays.” 
“ We took Archaster excavatus only on that one occasion; and the weather was so 
boisterous at the time that it was impossible to trace the early stages in the development 
of the embryo. It is evident that the process generally resembles that described by Pro- 
fessor Sars in Pteraster militaris; and it is quite possible that, while there is certainly 
not the least approach to the formation of a locomotive bipinnaria, as in that species some 
provisional organs may exist [at] an early period.” 
The specimen upon which these observations were made has been figured in PI. 
XXXI., a number of young in different stages of development are admirably preserved 
in situ, and may be seen protruding from amongst the paxille in the interbrachial 
regions. As noticed by Sir Wyville Thomson, it is in all cases the actinal surface which 
is first presented, and even whilst the young starfish is still resting entirely within the 
arcade-like spaces amongst the paxille and before any protrusion of the rays takes place, 
this appears to be the normal posture, 7.¢., the actinal surface uppermost. 
From the remarks above quoted it would appear that Sir Wyville Thomson was under 
the impression that the young were even at this stage actually attached to the parent by 
the centre of the abactinal surface, although he was unable to satisfy himself by what means 
this was effected. Like him I have failed to detect any organic or membranous connec- 
tion, and I am disposed to think that such did not exist. I make the remark, however, 
with all reserve and caution, for it would obviously be bold to dogmatise on the former 
existence of such a delicate connection, of which no trace remains after the specimen has 
been preserved in spirits for so long a time. I may further remark that not the slightest 
trace of any extension or projection of any of the larval tissues can be detected on the 
dorsum of a young individual of about 3 mm. in diameter, which I have reduced to serial 
sections, The pavxille of the abactinal surface are fully formed, and the epidermal or 
dorsal membrane, which covers the plates from which the paxillz spring, is continuous. 
The mouth also is fully formed, and the esophageal portion of the alimentary tract is 
capable of considerable protrusion. 
The form of the young individual is remarkable. The height is nearly as great as the 
total diameter ; the abactinal surface forms a subplane area excepting the slight round- 
ing or convexity along the median radial lines, whilst the actinal surface is prominently 
convex, with the mouth at the summit of the curvature, which slopes thence at a rapid 
angle of declivity to the extremity of the rays. 
The largest young one carried by the starfish under notice measures about R=3°5 
mm., and has ten or eleven pairs of tube-feet in each ray. There are four or five spine- 
lets on each adambulacral plate, one prominent into the furrow, the others forming oblique 
pairs behind it, though some may stand singly. The transverse disposition of the groups 
