THE SPEUMATOCENESIS OF DOMESTIC lI.V>nrAT.S. 235 



expect to find the iievccntage relation l.ctwecu the pairs showing any marked 

 valuation from tliat found betwtKHi tlio spermatogonia! pairs." 



But im stated above the observation of the chromosomes of the sperma- 

 togonia in the rabbit compelled us to recognize the folIo\ving facts: 1. Certain 

 chromosomes are considerably long and variously curved, and sometimes show 

 constrictions. 2. In those cells in which a largo number of chromosomes are 

 found, the smaller ones are very numerous. 



From these facts it is conceivable that as Hance ('17 b) has statetl of 

 the somatic cells of the pig, the cause of their variation is probably due to 

 the fragmentation of certain chromosomes. But it is ^■ery probable that this 

 fragmentation is not to ba lo^ked u[k)u as a normal process occurring in the 

 spsrmatogouia but is due to the influence of fixation. A striking evidence in 

 support of thus view is that, in materials which were poorly fixed, the variation 

 in numlier of chromos-.nuc^s was especially more numerous tnan in those which 

 were better fixed. 



n. The Synizesis and the Sy-vapsis. 



The s^'uizesis : — As mentioned above the shght polar aggi'egation of the 

 chromatin thfeads can always be seen in the early stage of the spermatocyte 

 in the mouse, while in the rabbit this aggregation is very conspicuous. 



It ts, however, difficult to determine whether this aggi-egation of the 

 chromatin threads represents the normal state which occm's in the cycle of the 

 spermatogenesis and is comparable to that of the horse and of cattle where 

 the conjugation of the chromosomes may occur, or whether this is regarded 

 as an artifact, being probably the result of the fixation. Doesberg ('08 a) 

 holds the latter view, where he says : " On pent aller plus loin et faii-o 

 remarquer que, si dans uu materiel bieu fixe on n 'observe pas de retraction© 

 de la chromatine, cet argument negatif a ime beaucoup grande valour que 

 Targument positif conti'airo ; car, s'il est impossible de mettre sur le compte 

 des reactifs Tabsence de sjTiapsis, nous savons au contraire (|ue les fixatem-s, 

 meme les meillem-s, pen vent dans de mauvaises conditions, produh'e le synapsis." 



1. In insects (Hemiptera), Wu,soN ('12) has stfttetl that the contraction figure can not ba 

 regnnleil ns an artifact. He proved that in some hemiptera this phenomenon is seen in the 

 living cell. 



