288 
Proceedings of Royal Society of Edinburgh. [sess. 
Such figures as those of Shipley * seem to indicate a later formation 
of archicoeles, and in a larva of Discina (?) figured by Joubin,t the 
mesoderm is distinctly segmented into four archicoeles. 
It seems likely that further work on these larvae will show a 
condition of the mesoderm, as in fig. 13. Apart, however, from 
these doubtful examples, it has been seen that the mesoderm in 
the adult is almost completely shut off into five cavities which 
correspond in major details with the segments derived from the 
larval segments. 
Again, it has been maintained that the larvae present four 
segments (c/., Shipley, Argiope , and Lacaze-Duthiers, Thecidium). 
Fig. 13. — Horizontal section through larval Argiope (partly after Shipley) ; 
the mesoderm is dotted and hypothetical. 
The former includes the developing peduncle (fig. 9), which may 
he regarded as a process of the metacoeles not of segmental value, 
and the latter includes a frontal portion of the protomere which 
hears the eyes. Neither can he said to have any claim to he 
regarded as segments. 
Lastly, the suggestion that the segments of the Brcichiopoda 
are at right angles to the primary oro-anal axis, appears to have 
even less foundation in fact than that the same is- the case in 
Phoronis.% In such a larva as that of Argiope the segments 
* Log. cit., pi. xl. figs. 33 and 35. 
+ Log. cit., pi. xiv. fig. 20. 
I Cf. Caldwell, Proc. Boy. Soc., 1883, and E. R. Lankester, Fncy. Brit., 
‘Polyzoa,’p. 171. 
