524 Theophilus s. Painter, 



somes. This small nucleolus shown in Fig. 30, will be discussed in 

 detail at a later time. 



Very late in this period the pachytene-threads seem to lose 

 their orientation and they lie scattered through the nuclear cavity. 

 Just at this time the accessory chromosome seems to disappear, but 

 a close examination of the cells will usually reveal this body lying 

 as a somewhat diffuse mass next to the nuclear wall. This loss of 

 staining capacity seems to persist for a short time after which the 

 accessory assumes its usual rod- like form. 



Diplotene stage. The time when the longitudinal split 

 appears in the pachytene-threads varies with the individual specimen. 

 It may happen that a very mature male will show all of the threads 

 split and the pachytene stages will be very rare, while in younger 

 specimens, just the reverse will be true. In the cell shown in Fig. 31, 

 we see the typical appearance of the diplotene- threads. The split 

 condition persists for a varying length of time and then a second 

 contraction sets in, when the autosomes take on the form which they 

 will have during the first maturation division. 



The processes going on in the diplotene-threads in Maevia vittata 

 are masked by the extreme contraction of the threads to one side 

 of the nucleus, so that it has not been possible to follow the forma- 

 tion of the autosomes in any detail. In another form Dolomedes 

 fontanus, q. v., it has been possible to trace the course of the con- 

 tracting diplotene-threads in the minutest detail. In Maevia as the 

 threads contract to one side of the nucleus one may see that the 

 two halves are tightly twisted together, but the origin of this 

 twisted condition could not be determined nor were later stages 

 illuminating. Following the second contraction we have the auto- 

 somes reappearing in the nuclear cavity with the shapes charac- 

 teristic of them during the first division (Fig. 32). 



During the diplotene stage and the second contraction the 

 accessory body retains its densely-staining character and seems to 

 persist unchanged. 



Prophase. As the autosomes emerge from the second con- 

 traction they take the stain veiy deep!}', but after long extraction 

 one may usually make out the form sliown in Fig. 32. At a slightly 

 later period, the chromosomes lie scattered through the nuclear 

 cavity and are most favorable for a study of chromosome morphology. 

 As this will be taken up in detail later, only one thing need be 

 pointed out here, namely, that in the different cells of this period 



