250 H. V. Wilson 



ing been retracted. In the freshly prepared tissue the flagella 

 are vibratile, the cells moving about. Soon however the flagellum 

 ceases to vibrate. 



3 The third class is not homogeneous. In it I include more 

 or less spheroidal cells ranging from the size of the granular cells 

 dow^n to much smaller ones. Many of these are completely 

 hyaline, while others consist of hyaline protoplasm containing 

 one or a few granules. 



Fusion of the granular cells begins immediately and in a few 

 minutes time most of them have united to form small conglomer- 

 ate masses which at the surface display both blunt and elongated 

 pseudopodia. These masses soon begin to incorporate the neigh- 

 boring collar and hyaline cells. One sees collar cells sticking 

 fast by the end of the long flagellum to the conglomerate mass. 

 Other collar cells are attached to the mass by short flagella. Still 

 again only the body of the collar cell projects from the mass while 

 there is no sign of the flagellum. Similarly spheroidal hyaline 

 cells of many sizes are found in various stages of fusion with the 

 granular conglomerate. In such a preparation the space under the 

 cover glass is soon occupied by innumerable masses or balls of the 

 kind just described, between which continue to lie abundant free 

 cells, some collar cells, others hyaline. Practically all the granu- 

 lar cells go to make up the balls. The play of pseudopodia at 

 the periphery of such balls, which results in the incorporation of 

 free cell's and in the fusion of balls to form larger masses, is easily 

 watched. Along with such a cover glass preparation it is cori- 

 venient to have some of the squeezed-out tissue in a watch glass 

 of sea-water. In the watch glass preparation it is instructive to 

 watch with a two-thirds or one-half objective the fusion of the cell 

 conglomerates to form masses like those strewn on covers, slides, 

 etc. (p. 3). 



These observations on the early steps in the formation of the 

 masses of regenerative tissue make it plain that such masses are 

 composed chiefly of the spheroidal, granular cells (amcebocytes 

 or archaeocytes), but that nevertheless other cells, collar cells and 

 more or less hyaline cells also enter into their composition. I may 

 recall the fact that in the formation of regenerative masses in a 



