22O MARY T. HARMAN. 



Bridges ('17) confirmed the observations of Metz as to the 

 spermatogonial and oogonial pairing, but deduced the kind of 

 synapsis from his genetic data. 



The genetic behavior of Paratettix is very different from that 

 of Drosopliila. In the hundreds of matings of Paratettix not 

 a single instance of crossing-over has occurred. In accounting 

 for the hereditary behavior of Parateltix without a knowledge 

 of the cytological behavior Morgan has suggested the theory of 

 identical loci. As has been previously shown, at no time during 

 the growth period is there any indication of a double thread, 

 and also there is evidence of an end to end union of the chromo- 

 somes to form the tangled thread of the contraction figure. 

 Moreover at the end of the growth period the chromatin material 

 forms the diploid number of chromatin elements. Also these 

 chromatin elements agree in relative sizes to the spermatogonial 

 chromosomes. Undoubtedly these parts unite end to end. In 

 this case there is little chance for crossing-over, as only the ends 

 of homologous chromosomes come in contact with one another. 

 In view then of the cytological behavior, it seems more likely 

 that the series of multiple allelomorphs may be accounted for 

 by the kind of synapsis rather than by the theory of identical loci. 



The writer is well aware that there is not perfect agreement 

 as to how synapsis takes place in the Orthoptera, and even within 

 a single family of the Orthoptera. McClung ('14) has recently 

 reviewed the literature on the subject of synapsis in Orthoptera, 

 and Wenrich ('16) has summarized the results. Briefly those 

 who have described or assumed telosynapsis are: Montgomery 

 ('05), Syrbula; Stevens ('05), Stenopalmatus, ('05) Blatta, ('10) 

 Forficula; Wassilieff ('07), Blatta; Zweiger ('06), Forficula; 

 Davis ('08), Acrididae and Locustidse; Buchner ('09), Gryllus, 

 CEdipoda; Brunelli ('09), Gryllus., and ('10) Tryxalis; Sutton 

 ('02, ''03), Brachystola; Baumgartner ('04), Gryllus; McClung 

 ('05, '08, '14), various Orthoptera; Nowlin ('08), Melanoplus; 

 Pinney ('08), Phrynotettix; Robertson ('08), Syrbula; Carothers 

 ('13), Acrididae. Those who have assumed or described para- 

 synapsis are: Gerard ('09), Stenobothrus ; Morse ('09), Blattidse; 

 Stevens ('12), Ceuthophilus; Robertson ('15), Tettigidae; Ve- 

 jodvsky ('11-12), Locustidae; and Otte ('07), Locusta. In addi- 



