408 
ORIGINAL ARTICLES. 
development of the disc, however, has in the mean time made the 
connections of this sac more apparent. The integument has been 
inverted in the centre of the disc, and the inversion, gradually 
deepening, has formed a month communicating with the digestive 
cavity, and the vascular ring surrounding the mouth has become 
more distinct. Five well-marked vessels branch from this ring, each 
to the end of a ray, and the sac is distinctly seen to join the ring 
between two of the radial vessels. 
A. 
Tig. 3. Astemcantion violaceus (M. & T.) 
A. Early stage in the development of the embryo, showing the three pseud- 
embryonic water-feet. 
B. A further stage in the development of the starfish, a. the pseudembryonic 
appendage becoming absorbed and withering in connection with the central ring of 
the ambulacral vascular system. 
27. As in Brachiolctrict (§ 19), so in Astercicanthion, a portion only 
of the germ-mass is converted into pseudembryonic appendages. 
A large part is at once modified into the tissues of the embryo. 
Even this latter portion is however invested by a layer of sarcode, 
and, as the organism rapidly increases in size by absorption through 
the general surface, I think we are entitled from the analogy of other 
forms, to regard this sarcode investment as a special pseudembryonic 
absorbent-layer. 
This layer is continuous with the wall of the anterior vascular 
appendage. The branches of this organ are undistinguishable in 
structure and in function from the ambulacral part of the starfish. 
A fluid undistinguishable from the chylaqueous fluid of the ambu¬ 
lacral system moves in them with the same characteristic motion. 
The appendage is closed externally, no communication except by 
transudation existing between its cavity and the surrounding medium. 
At first it communicates with the general cavity of the embryo, but 
