92 HERBERT 9B. DURHAM. 
he does not show thereby that the uric acid he found there 
was excreted by the animal; it is possible that it arrived into 
the starfish’s stomach in the interior of small mussels, &c., 
whose excretory organs contain that body, and of which as 
food the starfish appears to be very fond ; anyhow, such a source 
of the uric acid must be eliminated before Griffiths’ conclusion 
can be accepted ; for obviously, if the presence of urates were 
demonstrated in the gastric contents of an individual who had 
recently supped off oysters, it would by no means follow that 
the stomach was the organ whereby the individual excreted his 
urates. 
Now, uric acid and its allies are by no means the only effete 
products excreted by animals which are known to get rid of 
these bodies; in reference to them, however, I feel inclined to 
agree with most authors in regarding the abundant osmosis 
that goes on in the animal sufficient to account for the excretion 
of the more soluble substances. 
Kowalevsky (No. 40) has shown that in Echinids the dorsal 
organ takes up carmine, whereby it differs from urate-excreting 
organs, which take up indigo-carmine. It will now be advisable 
to notice what evidence there is of an excretory process by 
means of wander-cells in other animals. 
Kolliker (No. 48) has shown that the pigment present in 
hairs, epithelium, and nails is derived from pigment-cells, 
which pass outwards from the cutis. He has investigated the 
point in many animals—man, anthropoid apes, cetaceans, &c. 
Karg (No. 87) has demonstrated, by grafting epidermis upon 
ulcers in white men and negroes, that pigment-cells wander up 
into the epidermis and cause the pigmentation. 
Riehl (No. 55) shows that in hairs the pigmentation is due 
to the intrusion of pigment-cells from the cutis into the epi- 
dermal layer in man; in a short paragraph he states that after 
cutaneous inflammation wander-cells containing yellow or dark 
brown pigment are seen in the cutis, whence they get into the 
stratum Malpighii. 
Ehrmann (No. 28) gives an account of the process in 
Amphibia and mammals. 
