ASSOCIATION OF CHROMOSOMES IN DIPTERA 249 



ing on the root-tips of Ricinus, Kuwada ('10) on Oryza sativa, 

 Tahara ('10) on Morns alba and M. indica, and Ishikawa ('11) 

 on Dahlia coronata all observed evidences of pairing in somatic 

 cells. The observations of the three Japanese authors are 

 particularly convincing because of the variety'' of sizes among the 

 chromosomes with which they deal, and the symmetry of the 

 pairs. Shortly afterward Gates ('12) records slight evidences 

 of pairing in Oenothera and expresses his belief that pairing 

 in somatic metaphases "is widespread in the sporophyte tissue 

 of plants" (p. 1004). During the same year Miiller ('12) in 

 a comprehensive study of metaphase pairing in plants figures 

 and describes the paired condition in more than a dozen species, 

 several of which had not been treated previously. Among 

 the species described by Miiller the following furnish convinc- 

 ing evidence: Najas marina, Galtonia candicans, Listera ovata, 

 Albuca fastigiata, Aloe Hanburyana, Eucomis bicolor, Bischor- 

 nerea superba, Bulbine annua, Nerine rosea, Muscari botry- 

 odes, Scilla bifolia, Chinodoxa Luciliae, and Hyacinthus orientalis. 

 It can hardly be said, however, that the conclusions of these 

 various authors have been received by cytologists without criti- 

 cism or opposition. True, most of the critics have been simply 

 sceptical, rather than openly antagonistic, but others have been 

 radically opposed to some or all of the conclusions. Chief 

 among the critics are Meves, Fick and Delia Valle on the one 

 hand, and Dehorne with his adherents on the other. Meves, 

 Fick and Delia Valle object to practically the whole chromosome 

 theory (Meves '07, '08, '11, etc.) and hence incidentally to the 

 hypothesis of chromosome pairing. Since it is not in the province 

 of this paper to consider the whole chromosome theory, only 

 the criticisms relevant to pairing will be reviewed. The others 

 have been repeatedly and completely answered by previous 

 authors (Boveri, Strasburger, Gregoire, Wilson, Montgomery, 

 etc.). Meves has presented the arguments of himself Fick and 

 Delia Valle relative to chromosome pairing, in connection with 

 a study of Salamandra ('11). As a result of this study, he 

 concluded that the chromosomes can neither be assorted into 

 pairs according to size, nor can they be said to arrange themselves 



