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Nachdruck verboten. 



The Spermatogenesis of the Domestic Chiclten 

 (Grallus gallus dom.)« 



By Michael F. Guyer. University of Cincinnati. 

 With 35 Figures (2 Plates). 



In a former paper the writer ^) described the main features in the 

 spermatogenesis of the guinea. The existence of a well-marked extra 

 chromosome, apparently comparable to the „accessory" or „odd" 

 chromosome of Tracheata was recorded together with the occurrence 

 of a curious double numerical reduction to one fourth the spermato- 

 gonial number of chromosomes, as determined for the pigeon by the 

 writer some years ago. 



Both of these phenomena occur likewise in the chicken. The 

 chromosomes in general are more difficult to observe satisfactorily than 

 in the guinea, because of an even more pronounced tendency to crowd 

 together and of a somewhat less constant relationship in size of the 

 individual chromosomes. The odd chromosome, moreover, shows more 

 irregularity in form and does not so frequently stand at one pole of 

 the spindle while the other chromosomes are still in the equatorial 

 plate, although it may often be detected in the plate because of its 

 greater elongation toward one pole, as in Fig. 8. 



Counting the spermatogonia! chromosomes was found to be almost 

 a hopeless undertaking. When formed they lie in a web of material 

 ^which takes stain almost as deeply as the chromosomes themselves, 

 so that it is almost impossible to decide where the investing plasma 

 leaves off and the chromosomes begin. Furthermore, they seem fre- 

 quently to fuse together more or less at their points of contact with 

 one another. In general it may be said that in late prophase of 

 division there is, judging from the projecting ends, a peripheral band 

 of from ten to fourteen chromosomes with others inside. Fig. 1 is 

 from a late prophase or an equatorial plate stage which showed seven- 



1) M. F. GuYER, The Spermatogenesis of the Domestic Guinea. 

 Anat. Anz., Bd. 34, 1909, No. 20 and 21. 



