The Spermatogenesis in Pentatoma up to tlie Formation of the Spermatid. 75 



somes is 24. In the 1st spermatocyte appear first a number of rings, 

 which subsequently, by change of form, become with more or less re- 

 gularity 12 dumbbell-shaped chromosomes. Whether each sphere of 

 a dumbbell-shaped element represents one segment of the spirem 

 thread, is not to be clearly deduced either from the description or 

 the figures. "Wir haben also in der Aequatorialplatte 24 Kugeln, eine 

 Zahl, welche ja bereits in den Aequatorialplatten der Ursamenzellen 

 vorhanden war. Bei den letztern waren jedoch alle 24 Körperchen 

 vom Pol aus gleichzeitig zu sehen. Bei den Spermatocytcn dagegen 

 sieht man vom Pol aus nur 12 Körperchen, indem die andern 12 

 hinter die erstem getreten sind. ... Ich fasse also die hanteiförmigen 

 Stäbchen, als welche man ja die Chromatinelemente betrachten könnte, 

 . . . als zwei Einheiten." In one abnormal case 24 separate chromo- 

 somes could be seen from the pole of the spindle. Thus the total 

 number of spherical elements is 24, but Pyrrliocoris seems to be unique 

 in that while some of these elements occur in pairs or threes in the 

 spermatocytes, others occur singly, and in the equatorial plate they 

 are always arranged in pairs, with the result that the elements which 

 were single at the start must have arranged themselves later into 

 pairs. From Henkinci's observations it may be concluded that 24 

 chromosomes (the normal number) appear in the 1st spermatocyte, but 

 that these become grouped into 12 pairs in the 1st monaster. The 

 1st division results in the separation of the 2 chromosomes of each 

 pair, and hence is a reduction division ; in the 2nd division each 

 chromosome divides into two, though it could not be determined whether 

 this be a transverse or a reduction division. The pairs of chromo- 

 somes in the equatorial plate of the 1st spermatocyte have the dumb- 

 bell-shape characteristic of those chromosomes of Pentatoma; but in 

 FyrrJiocoris some of these pairs are formed by the union of separate 

 chromosomes. Perhaps those spherical chromatin elements in the pro- 

 phases of division, which appear single, are really connected together 

 by a linin thread, like the two halves of each dumbbell-shaped chromo- 

 some in Caloptenus (Wilcox); if this were so, and each such pair of 

 single elements represented one segment of the spirem thread, then 

 each dumbbell-shaped element in FyrrJwcoris would be equal to one 

 chromosome, as in Pentatoma. But unfortunately the number of seg- 

 ments into which the spirem divides was not ascertained, there being 

 no figures showing intermediate stages between Fig. 16 (a resting cell) 

 and Figs. 17 and 18 (where rings are already present). Henking is 

 quite correct as to the valence of each dumbbell-shaped element, but 



