ON THE PHYSIOLOGY OF THE NUCLEOLI AS SEEN IN 

 THE SILK-GLAND CELLS OF CERTAIN INSECTS 



WARO NAKAHARA 



Cornell University, Ithaca, iV. }'. 



NINE FIGURES (tWO PLATES) 



CONTENTS 



1 . Int roduction 55 



II. Material and methods 57 



III. Observations and considerations 57 



A. Morphological 57 



a. Pieris rapae Linn 57 



b. Neuronia postica Walker 61 



c. Summary 63 



B. Chemical 64 



IV. Conclusions 66 



Bibliography 67 



I. INTRODUCTION 



The peculiarly shaped nucleus and the unusually large num- 

 ber of the nucleoh in the cells of silk-glands of certain insects 

 have attracted the attention of previous workers on the his- 

 tology of these organs, but detailed cytological vrork done in 

 connection with the process of silk secretion is rather limited. 

 . Marshall and Vorhies ('06) published a comparative study 

 of the cell-structure of the silk-glands of Platyphylax desig- 

 natus, a caddis-worm, under different physiological conditions; 

 Vorhies ('08) demonstrated the fact that the multiple nucleoli 

 are derived from a single nucleolus of the ordinary tj^pe in the 

 nucleus of the same insect, and noted the increase of the nucleolar 

 material with the growth of the nucleus. These two works 

 have shown that the nucleoli may take some important part 

 in the metabohsm of the silk-gland cell, but the exact r61e they 



