ON WANDERING CELLS IN ECHINODERMS. 85 
den Réhrchen enthaltenen Fliissigkeit durch die Reagentien 
herriihren: aber ihre Constanz und ihre Zellenstructur spricht 
aber gegen diese Auffassung: wahrscheinlich gehen sie aus 
einer bedeutenden Verdickung des Endotheliums des Rohr- 
chens hervor ” (No. 6, p. 589). 
I have not examined A. aurantiacus, and cannot quite 
understand what is here referred to; probably it is a patch of 
pigmented ccelomic epithelium, such as occurs also in Aste- 
rina gibbosa. However, from the curious woodcut in illus- 
tration of the description one might suppose that the cells 
described were in reality “‘spheruliferous” leucocytes forming 
a plug at the apex of the branchia previous to their diadermal 
wander. 
Cuénot (No. 4) says, “La couche épidermique extérieure 
renferme beaucoup de cellules glandulaires comme celles que 
nous avons décrites 4 propos des téguments:”’ it seems not 
unlikely that some of these “ cellules glandulaires ” may only 
be spheruliferous corpuscles: vide also Prouho (11), and ef. 
the corpuscles of Holothurians. The process of emigration is 
far better marked in the ambulacral branchie of the Urchin. 
Hamann (No. 1, Echiniden) has already both described it and 
hinted at its meaning. In his description of the gills he 
says, “Sie sind Ausstiilpungen der gesammten Korperwand 
anzusehen und morphologisch wie physiologisch gleich zu 
setzen den Kiemenblaschen auf dem Riicken der Asteriden.” 
This is more true than Hamann thought, for by means of these 
processes spheruliferous corpuscles are got rid of in both 
groups: when talking of these spheruliferous cells he remarks 
“da die Bindesubstanzschicht iitber und tber von ihnen? 
erfiillt wird, sowandern sie wahrschemlich aus dieser in das 
dussere Epithel, um vielleicht von hier nach aussen zu ge- 
langen ” (cf. taf. vi, fig. 12). 
I have observed the same process in Echinus sphera; 
when a portion of a branchia is removed and examined it will 
be seen that the apices are occupied by a dusky brown mass, 
and that scattered about in the wall are smaller masses of 
1 « Riformige, stark lichtbrechenden Kornchen erfillten Zellen.” 
