DAVIS: SPERMATOGENESIS. 129 
contrary to McClung, the insertion of the spindle fibers may be “‘termi- 
nal,” ‘“‘subterminal” or “median” as de Sinéty maintained. ‘This 
author also correctly described the halves of the rings as being pulled 
past each other during division. But I believe with McClung that 
de Sinéty 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 Sinéty believed, 
but separates the two univalent components. In short, in the case of 
the ring- and loop-shaped chromosomes my results agree with de 
Sinéty’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 superimposed upon each other as 
de Sinéty’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 division 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 (:04, :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 Moore (:05), Lerat (:05),; Wallace (:05) Stevens 
(:05 to :067) Wilson (:05 to :06), Nowlin (:06) and Zweiger (:06) 
for arthropods; Korschelt (95), Foot and Strobell (:05), and A. 
und K. E. Schreiner (:06, :067) for annelids; Schockaert (:02) for 
Thysanzoon; Struckman (:05) for Strongylus; and Dublin (:05) for 
Pedicellina. Grégoire (: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), 
Voinoy (:03), Gross (:04), and Blackman (:05, :05*, :06) for arthro- 
