214 First J\Iatunitioii Spindle of Allolobophora Fcieticla 



matin is shown in Plioto. Ill, Plate YII, where the germinal vesicle 

 is traversed l)v an extremely delicate chromatic thread or threads. Prior 

 to this stage we have found no structure in the germinal vesicles other 

 than the nucleoli, the entire nucleoplasm being uniformly chromatic 

 and obscuring all differentiation. The only indication of the presence 

 of the diffused chromatin being expressed by the fact that the nucleo- 

 plasm reacts to nuclear stains with much more intensity than it does 

 after its chromatin constituent has formed the spireme or chromosomes. 



This is true of eggs taken from the free end of the ovary, and the 

 earliest stages of those found in the receptacula. A comparison of 

 results obtained from dried germinal vesicles with sections creates the 

 suspicion that much of the structure seen in sections of these eggs in 

 the earlier stage may be due to fixation. Such artificial demonstration 

 of the chromatin is, however, instructive in showing how the accessory 

 nucleoli arise in close connection with the chromatin in widely separated 

 areas of the germinal vesicles, later fusing into the one accessory nucle- 

 olus typical of later stages. 



In sections, a more marked aggregation of the chromatin into' pro- 

 nounced chromatic filaments is shown in Photos. 22 to 25, Plate II, 46 to 

 49 and 59 to 62, Plate III, these filaments undoubtedly corresponding 

 to portions of the skeins shown in the dried germinal vesicles of Photos. 

 113 to 115, Plate VII. 



At the upper, right-hand periphery of the germinal vesicle of Photo. 

 30, Plats II, there are two isolated, loosely granular filaments, the 

 granules perhaps representing individual chromomeres, which are ob- 

 scured in the more dense chromosomes of Photos. 28, Plate II, 51, 52 and 

 64, Plate III. Later stages of chromosome formations are shown in 

 Photos. 68 to 72, Plate IV, and further stages of development in Photos. 

 85 to 89, Plate V. 



In dried germinal vesicles we see a much more intelligible evolution 

 of the chromosomes, — in Photos. 113 to 115, Plate VII, the delicate 

 chromatic thread or threads of Photo. Ill have contracted or fused into a 

 relatively thick spireme. This spireme divides transversely into bivalent 

 chromosomes, the character of each chromosome being clearly expressed 

 by transverse constrictions in the center, demonstrating that each bivalent 

 chromosome is composed of two equal parts. Photos. 114 and 115, Plate 

 VII, show a distinct longitudinal split of the spireme, and Photos. 116, 

 117, 119 to 130, Plates VII to IX, show the persistence of this split to 

 the chromosome stage, producing tyj)ical tetrads. 



In all our sections showing the stages represented in Photos. 68 to 70, 



