312 



GENERAL EMBRYOLOGY 



Protenor Syromasfas 

 Anasa Homo 



Y 

 X 



AscAris 

 lumbricoidfS 



t f t 



t(jtftit&ts Nezara T/iynnfa 

 Yiricfttfa Coenua Jiitaris catceata 



Y 

 X 



& 



Fttctt in 



Prionirfus Geiastocoris 

 5ine& 



A.cholla 

 ultisjbin osa 



Fio. 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. 



I 



a 



A 



I 



e 



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

 rhromosome with other chromosomes, in the Orthoptera. From Wilson, a, 6, 

 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). A. The same element 

 after its division, in the ensuing telophase. 



