THE EMBRYOLOGY OF THE PORIFERA. 221 



out pseudopodia towards the surface, which touch the 

 ciliated cells. The latter have in the meanwhile drawn 

 in their rlagella and become rounded. When the process 

 of an amoeboid cell reaches a ciliated cell it immediately 

 seizes it and devours it, after the manner of a phagocyte. 

 In this way all the ciliees in Spongilla, and the greater 

 number of them in Esperia and Reniera, become captured 

 by the amoeboid cells and carried into the interior of the 

 sponge. When full fed, so to speak, the amoeboid cells 

 retract their pseudopodia and become rounded, forming 

 a number of " groupes polynuclees " in the interior of 

 the larva. Each such group consists of a central vesicular 

 nucleus, that of the amoeboid cell, and round this a 

 number of brightly staining small nuclei, derived from 

 the ciliated cells. The latter, after being thus engulfed, 

 alter in appearance. Their protoplasm forms a clear 

 zone round the nucleus, but is often indistinguishable. 

 The nucleus contracts become opaque and uniform, stains 

 strongly with carmine, and has the appearance of a simple 

 granule. In fact these are the granulations which have 

 been mistaken by Maas and Gotte for yolk granulations. 



We now have the larva composed of cellules epider- 

 miques externally enclosing a parenchyma of interme- 

 diaires and groupes polynucleaires, each of the latter 

 being an amoeboid cell which has devoured a number 

 of ciliees. After a short time further changes go on in 

 the amoeboid cells. Their captured nuclei begin to swell 

 and to separate one from another. The amoeboid cell 

 as a whole begins to enlarge itself and become irregular 

 in form, sending out lobes which fuse with the similar 

 lobes of adjacent cells to form a vast syncytial network, 

 in the meshes of which are the cellules intermediates 

 of the larva. Where there are a certain number of 

 ciliees not captured by the amoeboid cells, they also 

 take a part in this syncytium. Some of the meshes of 

 the syncytial network close up, others expand to form 

 lacunae, the future canal system. The captured nuclei 

 of the ciliees travel to the surface of the amoeboid cells, 

 regain their former appearance, and begin to arrange 



