3l8 ROBERT H. BOWEN. 



of fixing and staining reagents, a review of which will be given 

 hereafter. For the present purpose, a few general notes will 

 suffice. 



For the purely topographic study of sperm formation, and for 

 working out the finer details connected with the transformation 

 of the nucleus into the sperm head, strong Flemming followed 

 by Fe-hematoxylin and any desired counter stain, is still the most 

 satisfactory technique. For the mitochondria I have tried a num- 

 ber of methods, but by far the best for most purposes is Benda's 

 well-known alizarin-crystal violet stain for which Euschistus has 

 proven rather favorable material. For the Golgi apparatus I 

 have tried all the better known methods, including those of Cajal, 

 Kopsch, and Gatenby, with all of which results more or less satis- 

 factory were obtained. None of them, however, proved of any 

 value in studying spermatogonia and early spermatocyte stages, 

 and they were almost equaly defective for the seprmatocyte divi- 

 sions. Fortunately, in the course of my experiments I found a 

 modification of the Kopsch method which proved to be very 

 selective in its action and made possible a complete study of the 

 Golgi apparatus in the earliest stages, and also throughout the 

 maturation divisions. A description of this method has already 

 been published (Bowen, '19), to which reference may be made 

 for the details. In subsequent statements, I will refer to this 

 method as " modified Kopsch." 



I would like to take this opportunity of acknowledging my 

 great indebtedness to Professor E. B. Wilson, who has placed at 

 my disposal his many preparations of Hemipteran germ cells, 

 and whose suggestions and kindly criticism have been oi inval- 

 uable assistance to me in the preparation of this paper. I am 

 indebted also to Dr. Franz Schrader and Mr. S. C. Bellinger for 

 assistance in the collection of material ; to Mr. H. G. Barber who 

 has identified much of my material ; and to Miss Helen Daniels 

 who has made careful copies of my original figures for the pur- 

 pose of this publication. 



OBSERVATIONS. 



I. Structure of tlic Testis and Stages of Spermatogenesis. 

 The progress of spermatogenesis may be followed most easily 

 by dividing the process as a whole into a series of more or less 



