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Mr. H. E. Durham. The Emigration of [Jan. 26, 



The corpuscles after their adhesion to the wall of the branchia 

 creep by their amoeboid movement through the ccelomic epithelium, 

 the connective tissue layer, and the epidermis to the exterior (fig. 1). 

 Thus a clump may be formed on the outer side of the branchia, and 

 the animal is freed from some of the irritating particles. 



In these clumps the corpuscles retain their individuality (fig. 2), 

 they do not fuse to form plasmodia such as Geddes* describes in the 

 so-called clotting of the perivisceral fluid of urchins ; indeed if such a 

 coalescence did take place the facility for their migration through 

 tissues would be considerably diminished. 



In cases where the emigration is proceeding exceedingly actively, 

 besides the isolated phagocytes that are seen at different depths in the 

 branchial wall on their outward journey, the apices of some of the 

 branchiae appear to be perforated by an aperture, which is entirely 

 filled up by a plug of phagocytes (fig. 3, p). It is clear that such a 

 result might be due either to a stretching of the wall by a simulta- 

 neous entrance of several phagocytes at a certain point and subsequent 

 intrusions of others between them, or to an actual rupture or carrying 

 away of part of the wall by the energy and magnitude of the 

 emigration round one patch. So far as can be made out from serial 

 sections the former of these alternatives holds good ; there seems, 

 however, to be no reason why the latter might not also take place. 



Since in preparing Echinoderms for sections it is usual to distend 

 them with the fixing fluid, I should mention that here such treatment 

 has been avoided. The specimens were aneesthetisized with chloral 

 hydrate, and the gills could then be removed in a distended state, 

 while moreover they remained distended after removal. 



To return to the subject : after their arrival at the exterior the 

 corpuscles retain their irregular amoeboid shape for a time. They 

 then become spherical and swell up and later they disintegrate, the 

 granules they contained being scattered free. 



It was found that besides the corpuscles containing Indian ink 

 particles in the extruded material, there occurred amoeboid cells 

 loaded with refringent granules (fig. 2, b) ; moreover it is not only in 

 the injected specimens that such corpuscles emigrate; for if a starfish 

 is kept in a vessel (into which fresh sea-water is constantly dripping) 

 it throws off from its surface a certain amount of a dirty brownish 

 slime. This slime contains large corpuscles with refringent granules 

 (fig. 4) which are apparently identical with those mentioned above, 

 and with those peculiar cells which occur here and there in different 

 parts of the animal, especially perhaps in the so-called " heart ; " they 

 are called " Plasma- Wanderzellen " by the Germans : I propose to refer 

 to them as " sphseruliferous " corpuscles. 



* ' Archives de Zoologie Experimentale,' vol. 8, p. 433. 



