158 
responding to what was found in the Echinocyanms larva. In 
these larvæ a quite different nervous system, lying at the upper 
side of the oral lobe, was discovered by M a c B r i d e. *) I regret not 
having examined the living Echinocyamus larva with regard to 
the possible existence in it of an apical nervous system like that of 
the other larvæ; in the preserved specimens I have not been able 
to find it, whereas it may be very distinctly seen in the Echino- 
cardium larva. This is a point of no small interest — whether 
both these different nervous systems may occur together in the 
same larva or the one excludes the other, and how the matter 
lies in the different larval forms of Echinoids. Further researches 
are required to solve this question. 
In the Ophiurid larvæ a larval nervous system, homologous with 
that of the Auricularias, was described by Metschnikoff. l 2 ) In 
my memoir on „Die Echinodermenlarven d. deutschen Siidpolar- 
Expedition 3 ) I gave a careful description and figures of the nervous 
system of Ophiopluteus graciiis (p. 90—91 ; Taf. XIII. Fig. 4—6; 
Textfig. 4). During my stay at the Swedish Zoological Station I took 
the opportunity of examining this structure on the living larvæ. 
Like the Echinocyanms larva they can easily be examined from 
above, when standing directly under the surface film; they do not, 
however, keep so quiet as to allow a camera drawing. The two 
figures, 6 and 7, represent the larvæ of Ophinra texturata and 
of Ophiocoma nigra drawn in this position. The nervous system 
is seen as a series of nuclei in the bottom of the oral region 
passing between the corners of the postoral and the preoral band. 
It is, of course, only the small middle part of the nervous band 
that can be seen in the view from above. Fig. 8 gives a diagram- 
matic representation of the arrangement of the two nervous bands 
in the Ophiurid larvæ. 
l ) E. W. M a c B r i d e. The development of Echinus esculentus, together 
with some points in the development of E. miliaris and E. acutus. Philos. 
Transact. Ser. B. Vol. 195. 1903. p. 302. 
E. W. M a c B r i d e. The development of Echinocardium cordatum. Part. I. 
The external features of the development. Quart. Journ. Mier. Sc. 59. 
1914. p. 480. 
*) E. Metschnikoff. Embryologische Mitteilungen iiber Echinodermen. 
Zoolog. Anzeiger. 1884. p. 47. 
3 ) Deutsche Siidpolar-Expedition 1901 —1903. Zoologie VI. 1913. p. 91. 
