242 
E. W. MACBEIDE. 
figure. The praeoral (pr.o.), antero-lateral ( a.l . ), postero- 
dorsal (p.d.), and post-oral arms ( p.o .) are seen to be perfectly 
normal, except that, as frequently happens with larvae that 
are reared throughout their whole larval existence in half- 
gallon jars, they are somewhat shorter than usual. The two 
ventral ciliated epaulettes have met in the mid- ventral line 
above the anus, and behind and partly obscured by them 
are seen the dorsal epaulettes. Above the united ventral 
epaulettes can be seen the mid-ventral portion of the ciliated 
band, whilst below them can be seen the right and left 
posterior ciliated epaulettes, which are characteristic 
of the larva of Echinus esculen tus, and serve to distinguish 
it from the larva of Echin us miliar is, whilst at the posterior 
pole of the larva can be seen one of the three pedicellariae 
(joed.), which appear before the larval phase has been passed 
through. The other two are situated on the right side of the 
larva, and one of these (ped. 1 ) can also be seen. Although 
partly obscured by the mid-ventral portion of the ciliated band, 
the larval mouth (st.) can be seen. It is obvious that the 
larva before us represents what the larva of Echinus 
miliaris, which has been just described, would have grown 
to had it been permitted to live. The difference between the 
two (apart from the specific differences between the larvae of 
Echinus miliaris and Echinus esculentus) consists 
merely in the greater growth of the “ echinus-rudiments” in 
the case of the second larva. When this larva came into my 
hands it had attained the age of fifty-five days ; the larval arms 
were being absorbed, and the roofs of the amniotic cavities 
had also been absorbed, so that the tube-feet on either side 
were exposed ; in a word, the larva had attained the stage 
where, if it had been a normal larva, it would have meta- 
morphosed into a young sea-urchin. 
Fig. 3 represents a view of the larva in this stage seen 
from the left side. The oral lobe, carrying the praeoral and 
antero-lateral arms, is seen above, and beneath the praeoral 
arms the larval mouth and the oesophagus with the adoral 
ciliated bands can be seen. Below the oral lobe the body of 
