Spermatogenesis in spiders. 539 



chromosome counts possible, while the slide from which Fig". 68 was 

 taken, had been stained much more heavily. 



Leptotene stage. During- the rest period, the autosomes 

 have persisted as a very diffuse reticulum, but toward the end of 

 this period they begin to collect in knots, as was found to be the 

 case with Maevia vittata. The leptotene-threads are thin, slightly 

 irregular in outline, and a very large number of them are present 

 in the cell. 



During the leptotene period the accessory chromosome appears 

 usually as two rods staining very deeply, though these rods may 

 be more or less fused in different cells. We find in addition to the 

 accessory elements a varying number of smaller bodies lying scattered 

 through the leptotene-threads. 



These represent the very small nucleoli found in the rest period, 

 and are planosomes, as we shall see by their later behavior. 



Synizesis. The synaptic contraction is very marked, but the 

 leptotene-threads are so numerous that it has not been possible to 

 follow their course in any detailed way. The hétérochromosome 

 elements are usually drawn to one side of the nucleus with the 

 leptotene-threads, but we often find planosomes lying free in the 

 nuclear cavity. 



Pachytene stage. The accessory chromosome usually appears 

 as two rods lying close together, but these rods may form very 

 curious figures. In Fig. 69, the accessory elements form a very 

 much elongated loop. Throughout the pachytene period the accessory 

 chromosome retains its compact form and its affinity for the stain. 



The supernumerary elements show some variation in their 

 behavior. Usually we find a number of these bodies lying free 

 among the pachytene-threads, as shown in Fig. 69, although, in some 

 cases, the supernumeraries were collected around the accessory 

 chromosome elements. In the latter event there seemed to be no 

 fusion between the two types of bodies. 



One further point of interest, shown by Fig, 69, is the early 

 appearance of the centrosome, marked "cew", 



Diplotene stage. After the pachytene-threads have retained 

 their loop-like shape for a time, they lose their orientation towards 

 the accessory chromosome and lie very irregulary through the 

 nuclear cavity. It is about this time that the longitudinal split 

 appears. 



There are two points of considerable interest brought out by 



