312 



GENERAL EMBRYOLOGY 



Y 

 X 



Protenor 

 Anasa 



Syromasfas 

 Homo 



As car is 

 [umbricoides 



fr i i t 



Ncznra Eitschwtu.t Nezara ThyflK 

 Yiricfala Coenus /lifaris 



catceata 



Y 

 X 



Prionitfus Getas tocoris Acholla 

 5inea. 



nosa 



FIG. 145. Diagrams illustrating some of the variations in the X- and Y- 

 chromosomes. From Wilson. X, either as a simple or as a multiple element, 

 may or may not be paired with a Y-chromosome. 



L 



A 



t 



e 



Fio. 146. Compound chromosome-groups, formed by the union of the X- 

 chromosome with other chromosomes, in the Orthoptera. From Wilson, a, b, 

 after de Sinety, others after McClung. a. Triad group, first spermatocyte 

 division of Leptynia, metaphase. 6. Division of similar triad in Dixippus. 

 c. Triad group formed by union of the X-chromosome with one of the bivalent 

 chromosomes, first spermatocyte prophase, Hesperotettix. d. The same element 

 from a metaphase group, e. The same element in the ensuing interkinesis. 

 /. The compound element of Mermiria, from a first spermatocyte prophase. 

 g. The same element in the metaphase (now, according to McClung, united to 

 a second bivalent chromosome, to form a pentad element), h. The same element 

 after its division, in the ensuing telophase. 



