20 ClironioHomcs and Sex in Abraxas ■ 



be correlated with the extra chroincisdine fnuiid in one female of this 

 family, the (jrossidoriata bearing chromosome having become separated 

 abnormally from the scx-chromosomc. 



6. In the section on the maturation of the egg three cases are 

 described of eggs which have two nuclei, both undergoing maturation 

 simultaneously. In each case the two maturation figures are in exactly 

 the same stage ; in two they are in the equatorial plate stage of the 

 second polar mitosis, in the third egg both figures show three polar luiclei 

 and conjugation of the egg-nuclei with sperm-nuclei. It is suggested 

 that such an egg, if it had developed, might have given rise to a 

 bilateral gynandromorph, and th;it such gynandromoi-phs perhaps arise 

 in this way. In the egg in which there are two pairs of conjugating 

 pronuclei, the sperm -radiations are sinuous and branch, and those of 

 one system cross those of the other. 



Cambbidoe, 



January, 1911. 



EXPLANATION OF PLATES. 



All the microscopic tif^ures, witli the exception of No. 18, were drawn with Zeiss 3 mm. 

 apochromat. objective, n. ap. IIO, and with compens. ocular 12. The drawings are free- 

 hand, and are not all on exactly the same scale. 



PLATE I. 



Fig. 1. Wild ■? . Oogoiiial eijuatorial plate, .')6 chromosomes. 



Fig- 2. „ „ „ 55 



Fig. 3. ? of '12.18. „ ,, 55 



Fig. 4. Another ? of '12.18. Equatorial plate of cell in synapsis zone of ovary, 



55 chromosomes. 

 Fig. 5. ? of '12.31. Enuatiirial )ilate of cell in synapsis zone of ovary, 55 chromosomes. 

 Fig.fi. Same ? of '12.31. Oogonial equatorial plate, 55 chromosomes. 

 Fig. 7. ? of '12. 2U. Oogonial equatorial plate, .55 chromosomes, the double chromosome 



marked x is almost certainly one dividing. 

 Fig. 8. ? of '12.21. Oogonial equatorial plate. The small rings above the chromosome 



group indicate stained bodies which are certainly not chromosomes. 

 Fig. 9. i of '12.18. Spermatogonial plate with 50 (cf. Figs. 3, 4, oogonial plates with .55 



from females of the same brood). 

 Fig. 10. a, outer; h, inner equatorial plate in egg of a wild ?. 28 chromosomes in 



each plate. 

 Fig. 11. Egg of '13.4. a, outer polar plate with 28; b, inner with 27 chromosomes. 

 Fig. 12. Egg of '13.34. », outer polar plate, with 27 in one section and one lagging 



chromosome (separated from the rest by a line) in the next -section; h, inner polar 



plate with 27. 

 Fig. 13. Egg of '13.48. a, outer polar plate with 27 ; h, inner with 28. 



