50 THOS. H. MONTGOMERY jr., 



frequently it has approximately the form of a mushroom , with a 

 "stem" projecting into the nuclear cavity, and a thickened "head" 

 lying within the conical projection of the nuclear membrane (Figs. 151, 

 152, 159) ; in this case the "stem" of the mass is usually lighter at 

 the core than at the periphery. When present, it always fills the 

 projection of the nuclear membrane, but appears to be absent in some 

 cells of the smaller generation (where likewise the conical projection 

 of the nucleus is not always present). It is very probable that these 

 masses of substance represent remnants of the true nucleolus, with 

 which they agree in consistency, and in reaction to stains. In the 

 resting 1st spermatocytes (PI. 2, Figs. 95 — 10) the nucleolus is usually 

 single, and always lies within the nuclear cavity in close apposition 

 to the chromatin strands. In the succeeding dense spirem stage, when 

 the chromatin loops move to the periphery of the nucleus, they carry 

 the nucleolus along with them, it still being in contact with one, so 

 that the nucleolus reaches the nuclear membrane (n, Figs. 104, 113, 

 116, 117). In nuclei of the loose spirem stage I was seldom able to 

 find traces of the nucleolar substance, but occasionally observed small 

 masses close to the nuclear membrane, which probably represented 

 portions of the nucleolus. But how this substance comes to lie so 

 regularly within the conical projections of the nuclear membrane, could 

 not be determined : the nucleolus may be traced on its course to this 

 membrane, but no further. The identity of the two substances, how- 

 ever, is rendered very probable by their similarity in appearance. In 

 a few instances there was noticed on the outer surface of one of the 

 nuclear projections, i. e. close to the centrosomes, an exactly similar 

 mass (Fig. 153) ; most probably the latter represents some of this 

 substance which had exuded through the nuclear membrane at that 

 point. This substance is more voluminous in amount, and more 

 regular in occurrence , in cells of the large than in those of the small 

 generation; which accords with the fact that the nucleolus is larger 

 in the former than in the latter. Wilcox ('95) described in spermato- 

 cytes of Caloptenus the wandering of the nucleolus towards the peri- 

 phery during the prophase; but then he concluded that the nucleolus 

 divided into two, one part becoming a centrosome. In Pentatoma the 

 centrosomes appear at some distance from the nucleus, while the 

 nucleolus is still found in the nuclear cavity; and the possibility of a 

 true nucleolus standing in any connection with a centrosome seems 

 to me very doubtful, when we bear in mind the mode of origin and 

 economy of nucleoli (in a previous communication of mine, '98, have 



