No. 2.] COMPARATIVE CYTO LOGICAL STUDIES. 



0^3 



Form. 



A Single 



NUCLEOLUS. 



More than One Nu- 

 cleolus, All Alike. 



Nucleolus and 

 Paranucleolus. 



Psammechinus 



Echinocardium 



Echinus 



Toxopneustes 



Asteracanthion 



Sphaerechinus 



Amphidetus 



Solaster 



Ech in odermata . 



(Dergh) 



*■) 



)■ (Ludwig) 



\ (Hacker) 



:} 



(O. Hertwig) 



Chaetoderma 

 Proneomenia 



Mollusca. 



* (Wiren) 



*■ (Hubrecht) 



