SPERMATOGENESIS OF PASSALUS CORNUTUS. 427 



ABBREVIATIONS. 



c., centrosome; m., mitochondria; N., Nebenkern; 5., spindle derivative. 



All drawings were made with the aid of a camera lucida at table level using a 

 Zeiss 12 ocular and a 2 mm. oil objective. The reproductions have been reduced 

 one-third. 



