Papers from the Marine Biological Laboratory at Tortugas. 235 



SUMMARY. 



1. The apyrene spermatozoa of Strombus, in the adult condition, are 

 devoid of any nuclear material. The body of the spermatozoon is spindle- 

 shaped and is filled with large hexagonal albuminous bodies. Locomotion 

 is brought about by means of the undulations of two broad membranes 

 attached to each side of the body. 



2. Together with the eupyrene spermatozoa, they are found in the 

 uterus of the female, where they undergo certain katabolic changes resulting 

 in the total exhaustion of the albuminous bodies. They are never found 

 in the seminal receptacle, even when the latter is crowded with eupyrene 

 spermatozoa. 



3. The differentiation between the eupyrene and the apyrene spermato- 

 zoa can be traced back further than the growth period. In fact, apyrene 

 spermatozoa develop from cells which can be distinguished from the sper- 

 matogonia of the first generation and which have been named the apyrene 

 spermatoblasts. 



4. The apyrene spermatoblasts are believed to arise from the basal 

 nuclei. Confirmation of this phenomenon in other related forms is required 

 before it can be considered an established fact. 



5. The very early appearance of a centriole in the apyrene spermato- 

 blast establishes the polarity of the apyrene spermatozoon. 



6. The growth of the apyrene spermatoblast is marked by a great in- 

 crease in the volume of the cytoplasm and nucleus and by the development, 

 from the original centriole, of a very large centrosome containing many 

 secondary centrioles at its periphery. No division of any kind takes place 

 during the development of the spermatoblast. 



7. After the apyrene spermatoblast has acquired its full growth, the 

 dissolution of the nuclear membrane and the disappearance of the centro- 

 some take place simultaneously. The chromatic fragments (karyomerites) 

 are scattered throughout the distal half of the cell and the centrioles become 

 grouped beneath the membrane at the base of the cell. From each of the 

 latter a flagellum grows out. The cell may now be spoken of as the apyrene 

 spermatosome, for the ensuing changes give rise directly to the adult 

 apyrene spermatozoon without any appreciable increase in its volume. 



8. The centrioles divide and the distal halves move across the cell in 

 the direction of the chief axis, forming a bundle of axial fibers between 

 themselves and the proximal halves. At the same time the karyomerites 

 become vesiculated and remain active for a time, gradually becoming larger. 



9. The mitochondria which have been formed around the centrosome 

 during the growth period now constitute the inner margin of a ring of dense 

 cytoplasm which lies around the bundle of axial fibers at its base. 



10. When the bundle of axial fibers has come to extend entirely across 

 the cell, the secretion of the albuminous bodies is begun in the anterior por- 

 tion of the spermatosome. This process continues hand in hand with the 

 degeneration of the chromatic vesicles, until, successively, the middle and 



