ON WANDERING CELLS IN ECHINODERMS. 121 
EXPLANATION OF PLATE I, 
Illustrating Mr. Herbert E. Durham’s paper “‘ On Wandering 
Cells in Echinoderms, &c.; more especially with Regard 
to Excretory Functions.” 
Fie. 1.—From a section of tissues taken from a specimen of Dytiscus ten 
days after injection of Indian-ink particles into the abdominal cavity. Two 
nodules, in close approximation, are seen; the central mass of the left-hand 
nodule consists of distinct leucocytes, containing carbon particles; in the 
centre of the right-hand nodule are a few scattered nuclei, but the abundance 
of the carbon prevents many being well seen. Surrounding the central masses 
is the zone of crescentic cells, some with carbon particles; on the free surface 
of this capsule are a few unaltered leucocytes, most of which contain carbon. 
Fat = cell of fatty body. rach. = small tracheal tubes cut in the neigh- 
bourhood. Cam. luc., 2 in., oc. 2; some details filled with 3. in. oil imm. 
Fig. 2.—From a section of the madreporite of an old specimen of Spa- 
tangus purpureus. m.ep. Epithelium lining the madreporic tubule. 
6. Non-pigmented spheruliferous corpuscle. Pigment-holding corpuscles are 
seen passing through the epithelium. m. z. are nuclei of the madreporic 
tubule epithelium, which have been carried before the intruding pigment- 
corpuscles. The nuclei of the epithelium of the madreporic tubules are 
pencilled ; other nuclei are tinted purple. The colour of the granules is fairly 
correct. Cam. luc., 4 in. obj., oc. 2. 
Fig. 3.—From section of skin of Amphidotus cordatus, showing 
migration of pigment-cells through external epithelium. wz. indicate nuclei 
of pigment-cells. c.¢. Connective tissue. ep. Epithelium. Cam. luc., 
2 in., oc. 2. 
Fic. 4.—Isolated strands of dorsal organ of Asterias rubens, fixed with 
gold chloride and dissected out under a lens. di/. Dilatations. ana. Anas- 
tomoses. Cam. luc., 1 in., oc. 2. 
Fic. 5.—Part of an isolated strand of dorsal organ of A. rubens. Note 
the reticulum of cells on the surface of the dilatation (di/.). Cam. luc., 2 in., 
oc. 2. Weak chromic acid, picro-carmine. 
Fies. 6 and 7.—From sections of the siphonal portion of the mantle of 
Anodonta. The cilia are not preserved. Z,, Z, point to aggregations of 
pigment-granules which have reached the free surface (? pigment-corpuscles). 
ext.—zx. Points to the free external surface. conm. tiss. Connective tissue. 
p.g.¢. Pigment-cells, situate in the connective tissue. p.g.c’ (in Fig. 7). 
Two corpuscles containing orange-brown granules. Notice the outward- 
pointing pseudopod in one of them. e. pig. Pigmented epidermal cells, 
a. Nuclei of epidermal cells. Cam. luc., 2; oil immersion, oc. 2. 
