126 bulletin: museum of comparative zoology. 



early growth period. According to Stevens (:06'^) and Nowlin (:06) 

 in various Coleoptera the numbers of polar loops is at first the same 

 as the somatic number of autosomes, but later one end of each loop 

 becomes free, the free ends then uniting in pairs. 



On the other hand a side to side union of the chromosomes during 

 synapsis has been described in mammals by von Winiwarter (:00, :02) 

 and Schoenfeld (:01); in Amphibia by Janssens (:05), A. und K. E. 

 Schreiner (:07); in fishes by Marechal (:04), A. und K. E. Schreiner 

 (:04, :05, :07); in insects by Otte (:06); in crustaceans by Lerat (:05); 

 in gastropods l)v Bonnevie (:05, :06); hi annelids by A. und K. E. 

 Schreiner (:06, :06''); in worms by Tretjakoft" (:04) and Marcus (:06). 

 The most detailed description of this type of conjugation has been 

 given by A. und K. E. Schreiner (:04 to :07) in a series of papers on 

 synapsis and maturation in various animals, in an avowed attempt 

 to find a common type of these phenomena which will apply to all 

 organisms. These authors find that in all the forms studied the num- 

 ber of polar loops is at first the same as the somatic number of chromo- 

 somes and only later is the number reduced to one half the somatic 

 number, the reduction being accomplished by two loops becoming 

 parallel and gradually fusing. They describe and figure the ]iarallel 

 approximation of the loops as taking place first near the pole where the 

 loops are attached to the nuclear membrane, and gradually extending 

 toward the opposite pole until the threads become connected through- 

 out their entire length. The two components of the double thread 

 thus formed then fuse into a single thread, which a little later splits 

 along the line of fusion, so that the conjugants again become separated. 

 The Schreiners find that the double thread is composed of a series of 

 granules arranged in pairs, as I have described for the Orthoptera; 

 but according to these authors one granule of each pair belongs to 

 each conjiigant, which means of course, that the chromosomes con- 

 jugate granule by granule, as the Schreiners (:07, p. 470) clearly 

 state. "Der Prozess, den wir die parallele Konjugation der Chro- 

 mosomen nennen, ist demnach nicht als eine Konjugation der Chro- 

 mosomen als Ganzindividuen, sondern als eine Konjugation der 

 homologen Chromatineijiheiten aufzufassen, und dieser Konjugations 

 t_\']:)us ist eben in der Zusammensetzung der Chromosomen aus ver- 

 schiedenen Einheiten bcdingt." 



I have alrcadv described at length mv reasons for believing that such 

 a method of conjugation does not occur in the Orthoptera, although 

 Otte (:06) has described it for Locusta. I have occasionally seen the 

 spireme threads lying parallel to each other in pairs near the distal 



