STUDIES ON INSECT SPERMATOGENESIS. 355 



SUMMARY. 



1. In Eitscliistus the mitochondria! material of the primary 

 spermatocytes occurs in the form of threads which are definitely 

 oriented toward the centrioles in the prophases of the matura- 

 tion divisions. 



2. Due to this very definite arrangement, the threads are so 

 distributed during the anaphases that each daughter cell contains 

 one half of the mitochondrial material. 



3. The mitochondria are not divided autonomously on the 

 spindle but as a result of their position or the mechanical action 

 of the constricting cell wall. 



4. The Golgi apparatus of the spermatocytes is extensively 

 developed, occurring in the form of scattered Golgi bodies. 



5. During the maturation divisions these bodies undergo a 

 process of autonomous fragmentation into dictyosomes which 

 are arranged in a definite relation to the spindle and are then dis- 

 tributed in equal groups to the daughter cells. The arrangement 

 and distribution of the Golgi elements during division is clearly 

 dependent upon the centrioles. 



6. In the spermatids the Golgi elements are condensed into a 

 single body, the acroblast, from which the acrosome of the mature 

 sperm is derived. 



7. The remnant of the acroblast (or Golgi remnant) ultimately 

 breaks free from the acrosome and is lost in the cytoplasm of the 

 tail probably taking no further part in the formation of the 

 sperm. 



8. The centrioles of the spermatid are, as in most (all?) ani- 

 mals, paired, and in this case remain in the " neck " region of the 

 mature sperm. 



On the basis of the facts brought out in this study it is sug- 

 gested that: 



1. The regularity in the division of the cytoplasmic elements of 

 the cell, as illustrated by the mitochondria and Golgi bodies of 

 Euschistus, is not the result of chance but is accomplished by a 

 definite mechanism focused in the centrioles, and may perhaps 

 partake of the nature of a meristic, as contrasted to a mass 

 division. 



2. The acrosome of the animal sperm is probably universally 



