S pcrnnatogcnesis 487 



Ceresa taurina 



Three species of Ceresa were found near Cold Spring Harbor 

 on the morning-glory vines and tall weeds, during the last three 

 weeks of July. Unfortunately the chromosomes of the spermato- 

 gonial plates in all three forms are too close together to make it 

 possible to count them. They all have the same reduced number 

 of chromosomes and a peculiar deposition of chromatin on the 

 nuclear membrane in the growth period. As this phenomenon is 

 most pronounced in Ceresa taurina, I shall give the details for 

 this form. In the contraction stage, the chromatin is massed at 

 one side of the nucleus in a number of darkly-staining loops with 

 their bases united in a dense flat chromatic plate, which stains 

 more deeply than the loops (Fig. 62). As the loops spread through 

 the nucleus, they stain less, making the contrast with the black 

 plate more intense (Fig. 63). In the rest stage (Figs. 64 to 67), 

 the reticulum does not take basic stains at all; the chromatin plate 

 appears in various forms, sometimes continuous and sometimes 

 broken up into two, three, or four parts. By the time a split spi- 

 reme is formed, it has been almost entirely dissolved (Fig. 68), and 

 in the prophases, no trace of it is left (Fig. 69). When these 

 masses dissolve, the odd chromosome becomes visible as a round, 

 smooth body (Figs. 67 and 68), which probably was concealed in 

 the midst of the chromatic plate as far back as the contraction stage, 

 but its presence was obscured by the similarity of its staining reac- 

 tion to that of the other chromatin. As to the meaning of this 

 deposition of chromatin on the nuclear membrane, it seems possi- 

 ble that it is basichromatin thrown out from the chromosome 

 loops in the contraction stage, and that it takes no part in the fur- 

 ther formation of the chromosomes, since it disappears before the 

 next division. The only case at all similar which I can find in the 

 literature is that of Gryllus campestris described by Voinov ('04). 

 He claims that all the chromatin is gathered into the "corps nucle- 

 inien double," leaving the non-stainable achromatic substance 

 spread through the nucleus, and that when the spireme forms, the 

 chromatin is added to it again from this structure. He neglects the 

 distinction between oxy and basichromatin, and thinks that when all 



