The Spermatogenesis in Pentatoma up to the Formation of the Spermatid. 1'j 



passes. The number of chromosomes can be counted only on pole 

 views (Figs. 33—37), and then not in every case, since frequently 

 they are very densely grouped ; where they are separated, the number 

 14 is always found. I have counted these chromosomes, in order to 

 eliminate any possibility of error , by drawing each one with the 

 camera, then counting those on the drawing. The chromosomes are 

 so nearly spherical in shape that it is exceedingly difficult to determine 

 whether their longitudinal axis is parallel to, or at right angles to, 

 the axis of the spindle; but a careful study of pole views of the 

 chromosomal plate shows the chromosomes to be slightly longer than 

 broad, from which it may be concluded that their long axes are 

 placed transversely to the axis of the spindle, and hence that their 

 division in metakinesis is probably a longitudinal one. But their form 

 approaches so closely to the spherical, that I am not positive of the 

 correctness of this conclusion. 



The spindle figure of the monaster stage is somewhat barrel- 

 shaped (Figs. 30, 31), the mantle fibres having a slightly curved 

 outline. On first view there appears to be a single thick mantle 

 fibre at each end of each chromosome. But further study shows 

 that each such element is in reality composed of two fibres; the 

 two may be in contact for their whole length, but frequently are 

 separated from one another at their point of insertion on the chromo- 

 some, so that it is at this place that one is best convinced of the 

 paired nature of the mantle fibres. Henking ('90) considered that 

 the mantle fibres of the spermatogonia are single and concluded that 

 since here each chromosome has one fibre at either end, the chromo- 

 somes of the first reduction division must be bivalent, since to each 

 of them two mantle fibres pass from each centrosome ; but his figures 

 of the spermatogouic mitoses show these fibres to have great thickness, 

 so that it is probable that, as in Pentatoma, each of them is really 

 double. As will be shown subsequently, in Pentatoma as in Pyrrhocoris 

 the mantle fibres to the chromosomes of the first spermatocytic division 

 are paired, and those to the second , single ; but it is nevertheless 

 probable that in Pyrrhocoris the mantle fibres of the spermatogonia 

 are also paired, so that the number of mantle fibres to a chromosome 

 cannot be taken as a criterion of the valence of the latter. 



The metakinesis (Figs. 38—41) shows the division of each of the 

 14 chromosomes. As a rule they divide simultaneously, though the 

 one case was noted where those at the periphery divided sooner than 

 those at the centre. 



Zool. Jahrb. XII. Abth. f. Morph. 2 



