DAVIS: SPERMATOGENESIS. 85 



102) forms an irregular flattened plate closely apposed to the nuclear 

 membrane. It is usually somewhat vacuolated and tapers at one end, 

 which is attached to the nucleus at the same point as the autosomes. 

 The monosome usually lies near the distal pole of the nucleus rarely 

 being distant more than 90° from it. During the following stage (c) 

 there is very little change (Fig. 34), but during stage / the monosome 

 undergoes a very interesting metamorphosis. At the beginning of 

 this stage the monosome forms an irregular flattened plate closely 

 applied to the nuclear membrane, and connected at one end with the 

 distal pole of the nucleus. A view of the monosome e^i face (Plate 7, 

 Figs. 103, 104) shows that it does not stain uniformly, but contains 

 several lighter areas, where it is probably thinner than elsewhere. 

 When strongly decolorized it can be seen to be composed of minute 

 deeply staining granules imbedded in a less deeply staining matrix. 

 At a little later stage (Figs. 105-107) the thin areas have become 

 broken through so that the monosome becomes converted into a loop 

 both ends of which are attached to the nuclear membrane at the distal 

 pole. At this time the monosome has a very ragged outline and stains 

 but little deeper than the other nuclear elements, so that it is often 

 difficult to distinguish it. 



During the entire growth period the mitochondrion can be distin- 

 guished as irregular masses sc^attered through the cytoplasm and stain- 

 ing with Bordeaux more deeply than the latter. Usually, it is especially 

 abundant at the distal pole of the cell, but also forms an irregular 

 layer around the nucleus. At first the amount of mitochondrion is 

 small, but it increases rapidly during the growth period and becomes 

 a conspicuous element of the cytoplasm. In material fixed with 

 Flemming's fluid the mitochondrion is much more conspicuous and 

 stains much more deeply than in Hermann material. In Flemming 

 material it is usually distinctly granular and in some cases fibrillar. 



The interzonal body, which lies at the distal pole, so closely re- 

 sembles the mitochondrion that it is often impossible to distinguish 

 one from the other. In most cases the interzonal body can be identi- 

 fied with certainty only where it can be traced into an adjoining cell. 



B. Arphia tenebrosa. 



1. Monosome. 



The spermatocytes in this species are very similar to those in Dissos- 

 teira, but are in some respects even more favorable for study. Plate 



