246. 



INTRODUCTION TO CYTOLOGY 



conjugation (E 2 ) and take the form of rod tetrads (F 2 ) like those described 

 by Ruckert and Haecker. While opening out in this manner the longi- 



Fig. 96.— Diagram showing the origin of the tetrad of chromatids (D) according to 

 Scheme A (Ai-Ci) and Scheme B (A2-C2), and the further transformation of this tetrad into 

 tetrads of five types (Fi-F b ) . 



tudinal halves of each chromosome may diverge where the two chromo- 

 somes remain in contact (#3), the tetrad eventually taking the form of a 

 cross (F 3 ) as in the cases described by Paulmier and by Foot and Strobell. 



