DAVIS: SPERMATOGENESIS. 129 



contrary to McCluno;, the insertion of the spindle fibers may be "termi- 

 nal," "subterminal" or "median" as de Sinety maintained. This 

 author also correctly described the halves of the rings as l)eing pulled 

 past each other during division. But I believe with McClung that 

 de Sinety was in error in maintaining that the ring- and loop-shaped 

 chromosomes are formed by the opening out of the halves of a longi- 

 tudinally split rod. In chromosomes of this type the inclosed space 

 does not represent a longitudinal division, as de Sinety believed, 

 but separates the two univalent components. In short, in the case of 

 the ring- and loop-shaped chromosomes my results agree with de 

 Sinety's as regards the division of these elements, but differ funda- 

 mentally with respect to their formation. In the case of the cross- 

 shaped chromosomes I agree with McClung when he says: "Where 

 the elements of one of these compound chromosomes intersect they 

 lie in the same plane and are not superim]:)Osed upon each other as 

 de Sinety's theory demands and his figures represent." 



Recently the eumitotic type of maturation has been revived by 

 Bonnevie (:05, :06), who finds that in Enteroxenos, while the chro- 

 mosomes conjugate side by side during synapsis, neither of the two 

 succeeding divisions separates the conjugants but both are true equa- 

 tional divisions. However, judging from her figures, this species is a 

 very unfavorable form in which to determine the plane of division. 



In the case of the pseudomitotic type, Korschelt und Heider dis- 

 tinguish a "prereduction," where the first maturation division is 

 reductional and a "postreduction," where the second di\'ision is the 

 reducing one. The prereductional type has been described by a 

 large number of writers among whom may be mentioned: Mont- 

 gomery (:03, :04), A. und K. E. Schreiner (:b4, :05, :07), Farmer and 

 Moore (:05), and Janssens (:05) for vertebrates; Henking ('91), 

 Paulmier ('99), Montgomery (:00, :01, :05 :06), Nichols (:02), Holm- 

 gren (:02) Farmer and INIoore (:05), Lerat (:05), Wallace (:05) Stevens 

 (:05 to :06") Wilson (:05" to :06), Nowlin (:06) and Zweiger (:06) 

 for arthropods; Korschelt ('95), Foot and Strobell (:05), and A. 

 und K. E. Schreiner (:06, :06'0 for annelids; Schockaert (:02) for 

 Thysanzoon; Struckman (:05) for Strongylus; and Dublin (:05) for 

 Pedicellina. Gregoire (:05), after an extensive review of the literature 

 in the case of both animals and plants, concludes that this type will 

 probably be found to be universal. 



On the other hand the postreductional type has been described 

 among others by vom Rath ('92, '95), McClung (:00, :02), Sutton (:02), 

 Voinov (:03), Gross (:04), and Blackman (:05, :05'', :06) for arthro- 



