424 E. L. SHAFFER. 



period, and in the later stages are found in the form of threads 

 (chondrioconts) which lie in the direction of the chief axis of 

 the cell. 



3. During the maturation divisions, the mitochondria en- 

 velop the spindle peripherally and are divided by the cell con- 

 strictions, so that daughter cells receive approximately equal 

 amounts. 



4. The mitochondria of the spermatid form the Nebenkern, 

 which later is pierced by the axial filament. As the latter grows, 

 the Nebenkern elongates, forming a sheath about it. 



5. Spindle remains are found forming connections between the 

 spermatogonia. The spindle remains of the last spermatogonial 

 division persist throughout the entire growth period of the 

 spermatocyte. 



6. A spindle derivative is found in the spermatid, a portion of 

 which gives rise to the acrosome of the spermatozoon. 



7. The centrosome of the second maturation division is carried 

 into the spermatid and gives rise to the axial filament of the 

 spermatozoon. The centrosome becomes so closely associated 

 with the nucleus that there is no well-defined middle-piece in 

 the spermatozoon. 



LITERATURE CITED. 

 Arnold, G. 



'08 The nucleolus and microchromosomes in the spermatogenesis of Hydro- 



philus piceus. Arch. f. Zellforsch., Band 2. 

 Conklin, E. G. 



"02 Karyokinesis and cytokinesis in the maturation, fertilization, and cleavage 



of Crepidula and other Gasteropods. Jour. Phila. A. N. S., vol. 12. 

 Cowdry, E. V. 



'14 The development of the cytoplasmic constituents of the nerve cells of the 



Chick. I., Mitochondria and Neurofibrils. Amer. Jour. Anat., vol. 15, 



No. 4. 

 '16 The general functional significance of mitochondria. Amer. Jour. Anat., 



vol. 19, No. 3. 



Duesberg, J. 



'10 Nouvelles recherches sur 1'appareil mitochondrial des cellules seminales. 



Arch. f. Zellforsch. Band 6, Heft i. 

 'n Plastosomen, "apparato reticulare interne " und Chromidial apparat. 



Ergeb. der Anat. und Entwick., Band 20. 

 '13 Plastosomes et "organ-forming substances" dans 1'oeuf des Ascidiens. 



Bulletin de 1'Acad. roy. de Belg. 



