STUDIES ON INSECT SPERMATOGENESIS. 317 



locomotion and for initiating the cleavage of the egg. It follows, 

 therefore, that if we are rightly to estimate the role of the sperm 

 in fertilization we must first gain a correct conception of the 

 processes leading to its formation. What structures are present 

 in the germ cells? How are they distributed to the spermatids? 

 What is the role of each in the differentiation of the sperma- 

 tozoon? It is from the standpoint offered by such questions that 

 these studies have been undertaken. It was originally intended 

 to publish the results in one complete paper, but the delays inci- 

 dent to printing at the present time have made it seem preferable 

 to publish them now in briefer form, to be followed later by a 

 more detailed account. This paper contains, therefore, a sum- 

 mary only of the more important points, especially such as bear 

 more immediately on certain general cell-problems. 



For this study the insects offer many obvious advantages, not 

 the least of them the fact that the history o-f the nucleus has been 

 so thoroughly studied in this group that a trustworthy outline is 

 already at hand upon which to work out further details. I have 

 accordingly drawn the material for this study from Hemiptera 

 belonging to the Family Pentatomida, of which the so-called 

 " stink-bugs " are common examples. Of many forms examined, 

 I have made use particularly of Murgantia histrionica Hahn, 

 and Euschistus euschistoides (=fissilis} Voll. Other species of 

 Euschistus and several other genera (Arvelius, Brochymena and 

 Nezara) have also been used in cases where some particular 

 point was presented with unusual clearness or afforded interest- 

 ing comparisons. Among these various genera minor differences 

 occur, but in general the phenomena are essentially the same, the 

 factor deciding the use of one or another genus for a given pur- 

 pose being usually the size of the cells. 



Much of the work published heretofore on the formation of 

 the sperm has suffered, obviously, from an insufficient technical 

 treatment. The extensive use of acetic acid in the fixative has 

 been the chief source of failure, as Gatenby has recently in- 

 sisted, for it has turned out that certain important cytoplasmic 

 structrues mitochondria and Golgi apparatus are both of lipoid 

 nature and hence easily destroyed by fat-solvents. I have tried 

 to obviate this difficulty by recourse to a very extensive variety 



