1888.] 



Amoeboid Corpuscles in the Starfish. 



329 



In the slime these sphaeruliferous corpuscles are seen in various 

 stages of disintegration, held together by a material of slimy 

 consistency which, is, at any rate in part, derived from the swollen-up 

 stromata of the corpuscles, some doubtless having origin in the 

 scattered mucous gland cells of the epidermis. Besides these 

 elements a holotrichous infusorian occurred, frequently in consider- 

 able numbers, swimming about and feeding on the freely scattered 

 granules. In connexion with this I might also note that on a large 

 percentage of the specimens of Asterias rubens observed at Saint 

 Andrews there crawled a species of Caprella. These Caprellae feed on 

 the above-mentioned slime ; and those which lived on specimens 

 treated with aniline blue presented particularly gay alimentary 

 canals. 



As regards the emigration of these spheeruliferous cells, it is interest- 

 ing to find that Hamann* has recently described and figured the pre- 

 sence of snch corpuscles in the wall of the ambulacral gills of Echinids ; 

 these are doubtless on their outward journey. I might also note here 

 that when the dermal branchiae of Asterina gibbosa are slightly, not 

 rigidly, distended, they move round and round, more or less circularly, 

 so that their apices rub against the neighbouring ossicles. This 

 movement might be interpreted as the expression of attempts to 

 remove emigrated corpuscles from their surface ; the branchiae when 

 removed showed sphaeruliferous cells in their wall. 



I hope to make further observations to help to elucidate the mean- 

 ing of this out-wandering of sphaeruliferous cells, about which at 

 present it is impossible to draw up any definite conclusions. I desire 

 now merely to note its occurrence. 



It seems evident, however, that the starfish has the power of 

 removing minute foreign particles introduced into its system ; and 

 it is conceivable that in nature such particles might gain admittance 

 to the ccelomic cavity when an arm is thrown off. 



It does not seem clear what becomes of insoluble foreign granules 

 when they are introduced into other animals, except in the case of 

 mammals; at any rate I have been unable to find any account of an 

 actual transportation to the exterior such as has been described 

 above. 



Over and above any respiratory function that the dermal branchia? 

 may have, they form from their structure convenient places for the 

 out-passage of scavenging amoeboid cells. Hamannf notes that their 

 nerve supply is very scanty; the well-being of a fine nerve plexus 

 would obviously not be added to by amoeboid cells traversing it. 



To summarise in a few words — minute foreign bodies introduced 

 into the body-cavity of the starfish are removed to the exterior by 



* ' Jenaisclie Zeitschrift,' vol. 21, p. 159, and Taf. VI, fig. 12. 

 t 1 Die Asteriden,' Jena, 1885 (p. 11). 



