CHROMOSOME NUMBER AND PAIRS IN AMBYSTOMA 209 



exists in paii's in the germinal line is e\ddenced by their behavior 

 during the maturation period. 



Montgomery ('01) presented evidence for the recognition of 

 pairs in the spermatogonia, basing his argument upon the signifi- 

 cance of the chromosome number in Euschistus. Sutton ('02) 

 showed by means of a comparison of many camera-lucida draw- 

 ings of spermatogonia! complexes of Brachystola magna that 

 these chromosomes form a duplicate series of lengths, and by 

 means of measurements with a pair of dividers that the chro- 

 mosomes of the early primary spermatocyte prophases are graded 

 into the same series of relative sizes. Meves ('11) interpreted 

 his measurements upon spermatogonia of Salamandra maculosa 

 as failing to demonstrate pairs. Meek ('12) has made linear 

 measurements upon the spermatogonia and secondary spermat- 

 ocytes of a number of animals, interpreting his results as con- 

 firming the claim of the existence of pairs. Robertson ('15, '16) 

 also supports this view with metrical data in certain Orthoptera, 

 and Hance TlVb; '18 a) confirmativelj^ interprets his measure- 

 ments in the germinal and somatic cells of Oenothera and the 

 pig. In unmeasured spermatogonial chromosomes of the Dip- 

 tera, Stevens ('08, '10, '11), Metz ('14, '16), and \Vhiting ('17) 

 show ^-ery convincing evidence of pairs for the homologues are 

 associated side by side. Wilson's ('06, p. 11) figures of Anasa 

 and Hoy's ('16, p. 336; '18) figures of Anasa, Epilachna, and 

 Diabrotica also support this conclusion. The majority of other 

 authors as a result of their general observations have expressed 

 the belief that the chromosomes exist as a duplicate series. 



Furthermore, the existence of pairs in the spermatogonia is 

 practically proved by parasynapsis where the chromosomes of 

 the last spermatogonial division unite side by side and remain 

 so until separated by the reduction division. This statement is 

 made possible by Wenrich ('16) who, besides confirming the 

 already numerous and all but conclusive evidences of parasynapsis 

 by Janssen ('05, '09), A. and K. E. Schreiner ('06, a and b; 

 '08, a and b), Wilson ('12), and many others, carries the demon- 

 stration a step further by actually tracing a well-marked chro- 

 mosome pair A (p. 76) continuously through every stage of 



