i6o 



Scientific Proceedings (39). 



be sufficiently large to fit the laryngeal opening closely so as to 

 prevent aspiration, and also to cause enough of the inspired air to 

 pass through the anesthetic container. If it is desired to reduce 

 the amount of dead space, it may be done by placing a suitable 

 exit valve in the tube near the mouth. 



If it is desired to mix a gas with the air in varying proportions, 

 it is only necessary to place a three-way cock of the kind described 

 at the juncture of the gas stream with the air stream. 



102 (512) 



Hybridization in a mutating period in Drosophila. 

 By T. H. MORGAN. 



[From the Department of Zoology, Columbia University.] 

 In the fourth generation of a pedigree stock selected for the 

 absence of a black shield on the thorax, a few individuals appeared 

 having dark specks on the sides of the thorax below the base of 

 the wings. Thirty-two individuals with specks appeared to 167 

 without specks. Again from one set of the latter a new brood was 

 obtained that gave 19 present to 286 absent, or 1 to 15. Isolated, 

 the new type bred true. These were mass results, and might have 

 been due to a few individuals in the culture transmitting the specks 

 on the wings, while the majority of the individuals might not trans- 

 mit this character. Isolated females, not virgins, gave the follow- 

 ing proportions: 



Absent. Present. 

 18 2 

 24 o 

 31 o 

 24 o 

 31 6 



Here the results might have been due to a single female pairing 

 to more than one male before isolation. Therefore, virgin females 

 and males were isolated in pairs from the same stock. The fol- 

 lowing records are typical results. 



Absent. 



Present. 



Absent. 



Present. 



Absent. 



Present. 



37 



15 



49 



14 



20 



1 



3 



1 



31 



5 



7 



1 



21 



0 



91 



0 



33 



I 



23 



0 



69 



0 



12 



8 



63 



16 



21 



18 



46 



7 



49 



0 



23 



1 



38 



0 



