AMOEBOID MOVEMENT OF SPONGE CELLS. 155 



abundant red pigment many dark yellow-greenish granules. 

 Both forms are able to put out rounded or sometimes elongated 

 pseudopodia and to display an active amoeboid movement. 



The second class consists of spheroidal dermal cells differing in 

 size from 8 to 3 microns in diameter. They move very slowly, 

 putting out short rounded pseudopodia. 



To the third class belong the collar cells or so called choanocy- 

 tes. They are partially dedifferentiated having lost their collars 

 but still possess a long slender flagellum which continues to 

 vibrate for at least three hours. 



The process of reunion of the dissociated elements of the sponge 

 tissue consists of following stages; sinking of the cells and adhe- 

 sion with one another, adhesion to the bottom, amoeboid move- 

 ment and coalescence of cells, movement and coalescence of 

 aggregates. The process of the formation of the aggregates can 

 be easily observed in a microaquarium or in a hanging drop on a 

 hollow slide. In both cases the globular aggregates are formed 

 within three to four hours, the difference being that in the 

 microaquarium the aggregates strongly adhere to the glass, 

 while in a hanging drop they remain floating. 



Among the different tissue elements of sponge the archaeocytes 

 are the most active; some of them may send out pseudopods 

 within a few minutes after the sponge was squeezed. They begin 

 to move as soon as they come in contact with the bottom. The 

 coalescence may even occur while the cells are still in suspension. 



The character of the amoeboid movement of both yellow and 

 red archaeocytes is the same ; the cells put out large hyaline pseud- 

 opods and creep in different directions. The inner granuloplasm 

 of the cells appears to be more viscous than their surface hyaline 

 layer. This can be easily observed when two cells come in con- 

 tact with one another. When two archaeocytes touch one another 

 their external hyaloplasm spreads out from both sides of the 

 line of contact and flows round their bodies. Sometimes one can 

 notice how the hyaloplasm is pressed away from the contact 

 line between the cells and surrounds their bodies. 



Often the archaeocytes lose small drops of hyaloplasm which 

 remain behind them indicating the route of the cell. Another 

 archaeocyte passing the same way may wipe out these drops 

 which coalesce with its protoplasm. 



