503 



^'accessory" or "odd" chromosome of such wide occurrence in the 

 Tracheata which brings about the production of two kinds of sperma- 

 tozoa and which by its discoverers is regarded as in some way con- 

 nected with the determination of sex. Another interesting feature is 

 the curious double numerical reduction from the spermatogonial number 

 of chromosomes brought about through a pairing of the chromosomes 

 both in the primary and in the secondary spermatocytes, thus paral- 

 leling the condition found in pigeons as determined by the writer some 

 years ago. 



While in the guinea as in the pigeon, the cells are small, the 

 chromosomal phenomena are more readily followed because there is 

 more range in the size of the various chromosomes and the accessory 

 has a characteristic comma or club shape which ordinarily renders it 

 easy of detection. The general order of spermatogenesis as well as 

 most of the minor details of the phenomena are so similar to the 

 kindred processes in the pigeon ^) that the writer has not considered 

 it necessary to repeat them in minutiae here. 



The material was fixed mainly in Gilson's or in Bouin's fluid. 

 All essential points determined from the study of sections were cor- 

 roborated through an examination of smear preparations, likewise fixed 

 in one or the other of these reagents and stained by the iron-haemato- 

 xylin method, or with Delafield's haematoxylin, followed in each case 

 by acid fuchsin as a counterstain. 



In the matter of counting the greatest difficulty was experienced 

 ■with the spermatogonia. In many cases when all other cells of the 

 preparation were well differentiated the dividing spermatogonia appeared 

 as but a smudge of black with here and there the ends of chromo- 

 somes bristling out. In the equatorial plate stage the chromosomes 

 seem to lie in a web or plate of material which stains more deeply 

 than the surrounding cytoplasm and which is difficult to decolorize 

 without at the same time extracting the color from the chromosomes. 

 However, sufficient number of fairly favorable prophase and equatorial 

 plate stages showing the individual chromosomes were found to strongly 

 indicate seventeen as the correct number. A camera lucida drawing, 

 as carefully executed as possible, showing the chromosomes of such a 

 stage is seen in Fig 1. While there is no fixed pattern for their 



1) M. F. GuYER, Spermatogenesis of Normal and of Hybrid Pigeons. 

 Dissertation, University of Chicago, 1900. Also published as Bull. 22, 

 University of Cincinnati, 1903. In case this earlier paper is inaccessible 

 to any investigator, the author will gladly supply copies as long as his 

 stock of reprints lasts. 



