The Spermatogenesis in Pentatoma up to the Formation of the Spermatid. 27 



are fibres, very clearly marked in the synapsis, which pass from the 

 inner surface of the idiozome through the nuclear membrane into the 

 nuclear cavity, where they attach themselves to the chromosomes 

 (Figs. 63, 66, 69, 72 — 74). I have not been able to determine whether 

 they really pass through the nuclear membrane to the idiozome, since 

 there is no intervening space between these parts; but they very 

 certainly pass from the chromosomes in a more or less parallel bundle 

 to the nuclear membrane at that portion where the idiozome is situated. 

 This bundle of fibres, to be clearly seen in every nucleus of the 

 synapsis, provided the idiozome lies in the plane of the section, prob- 

 ably represent the persisting mantle fibres, with possibly portions of 

 central spindle fibres. I have counted as many as 6 or 7 of them 

 on a section, though since all do not lie in one and the same plane, 

 there is probably a larger number present. Along one or more of 

 these fibres, chromosomes, or a row of chromatin granules may extend 

 themselves, and in such a case the cell shows one or more chromo- 

 somes projecting out from the mass of chromating towards the idiozome. 

 Or these fibres may have no chromatin substance extending along them, 

 and it is only in such cases that their fibrous nature may be clearly 

 determined. Close to the nuclear membrane, at the proximal ends of 

 these fibres lies a plate of chromatin, or a number of chromatin granules, 

 connected with the central chromosomal mass by achromatic fibres. 

 In the synapsis is thus found, in almost every cell, the large mass 

 of chromosomes near the centre of the nucleus, and, more or less 

 separated from them, a small peripheral layer of chromatin, close to 

 the idiozome (Figs. 58 — 75). The explanation for this excentric position 

 of a certain amount of chromatin, is given by the assumption of the 

 strong attachment of some of the chromatin substance to the mantle 

 fibres: so strong an attachment, that when the chromosomes have 

 grouped themselves together in the centre of the nucleus, a small 

 amount of their substance, probably that portion to which the mantle 

 fibres were attached in the preceding metakinesis, is kept at the 

 periphery of the nucleus by the tension of the mantle fibres. These 

 peripheral chromatin granules are not cast off entirely from the chromo- 

 somes, but before the end of the synapsis probably return to the central 

 mass of chromatin, since in the postsynapsis there are no evidences 

 of detached chromatin granules anywhere in the nucleus or the cytoplasm, 

 so that in this process there can be no reduction of chromatin mass. 

 These fibres, which our observations would show to be mantle 

 fibres, may throw some light upon the first origin of these elements. 



