DAVIS: SPERMATOGENESIS. 123 



chromatin occurs, the term has been used in a wider sense to apply 

 to the entire series of phenomena which are concerned in the conjuga- 

 tion of the chromosomes, and especially to the stage at which the 

 reduced number of chromosomes is first apparent. INIoore himself 

 (Farmer and Moore :05) has used the term in this somewhat modified 

 sense, where it is equivalent to his "contraction figure," and has 

 defined it as follows : — -"S}aiapsis represents that series of events which 

 are concerned in causing the temporary union in pairs of premaiotic 

 chromosomes, previously to their transverse separation and distribu- 

 tion, in entirety between two daughter nuclei." Used in this sense 

 the term will apply, in the case of the male germ cells at least, to the 

 greater part of the growth period, and especially to the stage of the 

 polar spireme. In fact, an examination of the literature leads to the 

 conclusion that the occurrence of the polar loops is the most character- 

 istic phenomenon of the synaptic period, and while in the present 

 stage of our knowledge it does not appear to be of universal occurrence, 

 yet this arrangement of the spireme threads is so common and occurs 

 in such widely separated groups as to indicate that it is of fundamental 

 importance. Indeed, I suspect it will be found to be the most char- 

 acteristic stage of the synaptic period. Montgomery (:00) seems to 

 have been the first to call attention to the fact that in the growth period 

 of the germ cells in many animals the spireme is in the form of loops 

 with their open ends directed toward the distal pole, where they are 

 more or less closely attached to the nuclear membrane. Such an 

 arrangement of the spireme during synapsis has since been described 

 in a large number of forms. Among others in mammals by von Wini- 

 warter (:00, :02); in amphibians by Kingsbury ('99, :02), Eisen (:00), 

 Montgomery (:03, :04), Janssens (:05), Moore and Embleton (:06), 

 and A. und K. E. Schreiner (:07); in fishes by Moore ('95), A. und 

 K. E. Schreiner (:04, :05, :07), Marechal (:04, :05), and by Farmer 

 and Moore (:05); in insects by de Sinety (:01), Baumgartner (:04), 

 Montgomery (:05), Farmer and Moore (:05), Stevens (:05^, :06''), 

 Nowlin ( :06) and Otte ( :06) ; in arachnids by Montgomery ( :05) and 

 Wallace (:05); in Peripatus by Montgomery (:00); in copepods by 

 Lerat (:05); in gastropods by Meves (:02) and Bonnevie (:05, :06), 

 and in annelids by A. und K. E. Schreiner (:06, :06"). In all cases 

 where the number of loops has been determined there is always, 

 as in the Orthoptera, at least during the latter part of the polar stage, 

 one-half as many loops as somatic autosomes. The above makes no 

 pretence to being a complete list, but is given to show the wide occur- 

 rence of the polar loops during synapsis. I have no doubt that a 



