400 
ORIGINAL ARTICLES, 
of these openings, but in specimens from Sicily he detected the 
nascent madreporic tubercle and sand-canal in the position of the 
second aperture, towards the margin of the disk, and he believed 
that the two apertures formed points of direct communication 
between the ambulacral vascular system of the starfish and spaces in 
the body of the pseudembryo. 
The perisom of the starfish was continuous with the body-wall of 
the pseudembryo. The most definite and permanent connection 
between the two organisms was by the oesophagus. Koren and 
Danielssen describe the final liberation of the starfish by the rupture 
of this attachment by forcible convulsions of the pseudembryo. 
12. In the autumn of 1850* Prof. Muller observed at Trieste 
another form of Bipinnaria , which had the advantage of passing 
through its metamorphoses with great rapidity; he was thus able to 
trace the earlier stages in the development of the Echinoderm embryo. 
In all important points of structure this pseudembryo resembled 
the forms previously described. The appendages were, however, 
much shorter, and the individuals were extremely minute, the smallest 
only t l of a line in length. The starfish began to appear when the 
pseudembryo was ~ 2 — of a line long. 
In its earlier stages the animal is of a glassy transparency. It 
contracts its body forcibly, but no trace of muscular tissue is per¬ 
ceptible. On the sides of the stomach there is at first a mass of 
granular blastema. This disappears by absorption as the pseud¬ 
embryo increases in size. 
13. Hear the middle of the dorsal 
surface, a little to the right of the 
oesophagus, a minute pore appears in 
larvae of a line in length. This 
f j pore passes into a narrow canal, which 
penetrates vertically the substance 
of the dorsal layer, and ends in an 
elongated sac, ciliated within, and 
charged with moving corpuscles. 
The sac lies beneath and to the side 
of the oesophagus, and sometimes a 
second portion of the sac passes back¬ 
wards, and may be seen on the right 
side of the stomach. The ciliated sac 
is subsequently undoubtedly in con¬ 
nection with the ambulacral system 
of the starfish, and the observations 
of Muller, especially those on the 
auricularian pseudembryos of the 
* “Ueber die Larven und die Metamorphose der Echinodermen. Berlin, 1852. 
Fig. 2. Bipinnavia observed at Trieste. 
a. Dorsal integument of the pseudembryo; b. ventral shield ; c. pseudcstome, 
