1880.] 



Amoeboid Cells into Plasmodia, fyc. 



253 



of the common shore-crab (Carcinus mamas). Fig. 24 represents a 

 few of both kinds of corpuscles of Cancer Pagurus, and fig. 25 a small 

 clot formed by the union of the finely granular corpuscles. In fig. 26 

 are represented some of the corpuscles of the common starfish (Astera- 

 canthion vulgare), showing the curious looped pseudopodia usual 

 among the Echinoderms. Figs. 27 and 28 are successive drawings of 

 a group of uniting corpuscles from the same preparation. As in 

 fig. 17, the development of large pseudopodia from the completely 

 fused mass is evident. 



But it is among the Echinoidea* that the phenomena of corpuscular 

 fusion occur on the most extraordinary scale. A good specimen of 

 Echinus splicer a furnishes perivisceral fluid enough to fill an ordinary 

 tumbler. The fluid is at first homogeneous and of a uniform pinkish 

 grey tint, but rapidly becomes cloudy. The cloud contracts constantly, 

 and so becomes gradually darker and of more defined form, and in 

 the course of a few hours shrinks into a small brown pellet. When a 

 drop of this fresh fluid is examined in the moist chamber, it is seen to 

 contain, in addition to its coloured amoeboid corpuscles, the same two 

 types of colourless corpuscles, the coarsely and the finely granular, as 

 have just been described in Pagurus (figs. 15 and 16). Here too the 

 clot is entirely due to the union of the finely granular corpuscles, which 

 almost instantly run into small heaps, these into larger, and larger 

 ones, and so on until we have a vast amoeboid mass, which rapidly 

 differentiates into endoplasm and ectoplasm, the former containing the 

 nuclei and granules of the constituent corpuscles, and the latter, pro- 

 duced by the union of their hyaline ectoplasm, forming a broad clear 

 margin, and sending out pseudopodia, sometimes blunt, but usually fila- 

 mentous. These pseudopodia frequently run out over such distances 

 that an adequate idea of their extraordinary size could scarcely be 

 given within the limits of the entire plate. 



The resemblance of all these cases of the fusion of amoeboid cells 

 taken from so many types of Invertebrata is too close to be accidental. 

 All the evidence points to the conclusion that the clot which appears 

 in any invertebrate corpusculate fluid is formed, always partly, and 

 sometimes wholly, by the fusion of the finely granular amoeboid 

 corpuscles therein suspended.! Thus, while the blood of a lobster is 

 still capable of clotting after removal of the corpuscles by filtration 

 (Fredericq), the perivisceral fluid of a sea-urchin is not. 



* A detailed account of the corpuscles of Echinus, &c, will shortly appear in the 

 " Archives de Zoologie Experhnentale." 



f With regard to the amoeboid corpuscles of vertebrates, I have not yet been able 

 to make any satisfactory observations. Ziegler has concluded from his researches 

 on the formation of giant cells in exudation liquids (Exp. Untersuch. ueber d. 

 Herkunft d. Tuberkeelmente, &c, Wiirzburg, 1875) that a coalescence of amoeboid 

 cells does actually sometimes take place. 



