86 HERBERT E. DURHAM. 
similar colour. These are collections of large cells containing 
refringent spheres; they break up very readily with slight 
pressure ; even in the fresh living condition they can be seen 
at various levels in the wall of the branchia as well as actually 
outside it. 
Much trouble was experienced in preparing sections where 
the epithelium was extensively infiltrated with spheruliferous 
cells, as appears to be frequently the case, because the cohe- 
sion of the epithelium is much diminished, and therefore it 
easily breaks up and disintegrates in the hardening and other 
preparatory processes. 
The spheruliferous cells found here differ from those which 
are found so abundantly in the dorsal organ, &c.—(1) in 
having a more dusky brown appearance, the majority of those 
of the dorsal organ, &c., being of a faint yellowish colour 
(corpuscules miriformes), and (2) in disintegrating very readily. 
So that there appears to be two forms of sphere-holding cor- 
puscles; in the dorsal organ one sees corpuscles containing 
some of the clearer and some of the more dusky spherules as 
well as some containing only dusky ones, besides the more 
abundant cells with the clearer cells; now as the dusky ones 
are found leaving the body through the branchiz it seems 
possible that they have performed their functions, whatever 
they may be, and are no longer of use in the economy of the 
animal: whether the bright orange-red pigment-corpuscles 
have any share also in the process of transformation I have 
not been able to determine. 
The spherules of the corpuscles found in the branchize 
stain very deeply with acid hematoxylin, as well as with aniline 
colours. Hamann pointed out that they stain with anilines 
but not with carmine, which my sections confirm. 
In the irregular Echinids (Spatangus purpureus and 
Amphidotus cordatus) the process of removal of products 
from the body by means of ameeboid cells is seen to be more 
defiuitely associated with pigment. In these forms there are 
some cells with pigments of a brighter colour which readily 
dissolve in alcohol, &c., and are not easily recognised in pre- 
