The Spermatogenesis in Pentatoma up to the Formation of the Spermatid. \'\^ 



"and they are further distinguished, from them by the fact that they 

 have only 12 chromatic rods, whereas the spermatocytes have each 

 24 spherical chromosomes". In the spermatocytes the nucleolus lies 

 near the centre of the nucleus, then it "moves to the periphery of 

 the nucleus, and meantime seems to have divided into two portions, 

 one of which passes into the cytoplasm, while the other remains in 

 the nucleus ; later, both parts appear outside of the nucleus and on 

 diametrically opposite sides of it". He considers the centrosomes to 

 stand in genetic relation with the nucleolus. Caloptenus: There are 

 12 rod-shaped chromosomes in the spermatogonia. In the prophase 

 of the 1st spermatocyte the spirem thread shows 24 collections of 

 chromatin on its surface ; it then breaks transversely into 12 segments, 

 each dumbbell-shaped segment thus produced consisting of 2 chromo- 

 somes connected together by a number of linin threads; these seg- 

 ments now become so arranged in pairs that 6 chromatin rings re- 

 sult, "by the fusion of the ends of the two parallel dumbbells". The 

 same result may be reached also by a different process : the transverse 

 segmentation of the spirem thread results "in the formation of twelve 

 segments with very irregularly serrated edges. These segments associ- 

 ate themselves in pairs. They are either so closely applied to each 

 other as to appear like single rods or else show two rows of granules, 

 and thus give the same appearance that would have resulted from a 

 longitudinal splitting of a single segment. The component halves of 

 these six segments separate from each other except at their ends, 

 and thus form rings .... The granules scattered along these rings 

 then collect into four chromosomes. The result is, therefore, the same 

 as by the process first mentioned". In the equator of the first spindle 

 the rings are transversely halved, and in the second spindle the dyads 

 are transversely halved. "The number relationships of the chromo- 

 somes in the spermatogenesis of Caloptenus may be thus tabulated: 

 Spermatogonia 12 univalent chromosomes 



Spermatocytes, 1st order 6 quadrivalent chromosomes 

 Spermatocytes, 2nd order 6 bivalent chromosomes 

 Spermatids 6 univalent chromosomes." 



Wilcox ('96) gives some additional observations on Caloptenus, 

 in corroboration of his previous ones. 



Wilcox ('97) upholds his opinions of the valence of the chromo- 

 somes, and the formation of the tetrads, in the spermatogenesis of 

 Caloptenus, against the objections of Wilson ('96) to the effect that 



