PORIFERA, CCELENTERATA, VERTEBRATA 71 



TABLE OF THE VARIOUS CLASSES OF CELLS IN SPONGES 



I. Epithelial stratum 



Dermal Layer { II. Porocytes 



III. Skeletogenous 

 stratum 



Gastral Layer IV. Gastral epithelium 



Archaeocytes 

 (primordial 

 cells) 



V. Amebocytes (wan- 

 dering cells) 



VI. Tokocytes (repro- 

 ductive cells) 



1. Pinacocytes 



(epithelial cells) 



2. Myocytes 



(contractile 

 cells) 



3. Gland cells 



4. Spongoblasts 

 { 5. Pore cells 



6. Scleroblasts 



7. Collencytes 



(stellate cells) 



8. Desmacytes 



(fiber cells) 



9. Cystencytes 



(bladder cells) 



10. Choanocytes 



(collar cells) 



11. Phagocytes 



(ingestive cells) 



12. Trophocytes 



(nutritive cells) 



13. Thesocytes 



(storage cells) 



14. Statocytes 



(gemmule cells) 



15. Gonocytes 



(sexual cells) 



blastula-like larva is formed (Fig. 27, A). At the 

 posterior pole two blastomeres (posterior granu- 

 lar cells, p.g.c.) remain undifferentiated ; they are 

 much larger than the other cells, are granular, and 

 possess vesicular nuclei. The larva becomes fixed 

 by the anterior pole, and during the metamorphosis 

 that then takes place, the two posterior granular 

 cells, the archeocytes, multiply rapidly, forming a 

 large number of minute cells which resemble certain 

 leucocytes. These are known as amebocytes. By 



